6b Draft EECA
Lower Duwamish Waterway Superfund Site Terminal 117 Early Action Area REVISED ENGINEERING EVALUATION/COST ANALYSIS DRAFT FINAL Prepared for: The Port of Seattle and The City of Seattle For submittal to: US Environmental Protection Agency, Region 10 1200 Sixth Avenue Seattle, WA 98101 January 19June 3, 2010 Prepared by: Dalton, Olmsted & Fuglevand, Inc. Environmental Consultants Table of Contents List of Tables v List of Figures vi List of Maps ix Acronyms and Abbreviations xiii 1 Introduction 1 1.1 CERCLA PROJECT PROGRESSION 2 1.1.1 Lower Duwamish Waterway and early action areas 5 1.1.2 Initial early action area investigations and 2005 EE/CA 5 1.1.3 2006 time-critical removal action 6 1.1.4 Inclusion of the Adjacent Streets 6 1.1.5 Dioxin investigations and PCB boundary refinement 6 1.1.6 Expanded T-117 EAA and the revised EE/CA 7 1.2 EE/CA ORGANIZATION 8 2 Site Characterization 11 2.1 SITE DESCRIPTION 11 2.1.1 Location and characteristics 11 2.1.2 Historical activities 12 2.1.3 Current site features 15 2.1.4 Current land use, zoning, ownership, and activities 22 2.1.5 Physical environment 24 2.1.6 Sensitive ecosystems and habitat 43 2.2 PREVIOUS REMOVAL ACTIONS 44 2.2.1 1999 time-critical removal action 45 2.2.2 2004 utility corridor cleanout 46 2.2.3 2006 time-critical removal action 47 2.2.4 Independent cleanup actions in the Adjacent Streets and Residential Yards Study Area 48 2.3 PREVIOUS ENVIRONMENTAL INVESTIGATIONS AND SUMMARY OF ENVIRONMENTAL DATA 49 2.3.1 T-117 Sediment Study Area 60 2.3.2 T-117 Upland Study Area 61 2.3.3 Adjacent Streets and Residential Yards Study Area 64 2.3.4 Groundwater 71 2.4 RECONTAMINATION ASSESSMENT AREAS 77 2.4.1 Basin Oil parcels 77 2.4.2 South Park Marina 80 Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page i 3 Streamlined Risk Assessment 83 3.1 CONCEPTUAL SITE MODEL AND PATHWAY IDENTIFICATION 83 3.1.1 Primary sources 84 3.1.2 Primary release and transport mechanisms 86 3.2 STUDY AREA-SPECIFIC TRANSPORT MECHANISMS, RECEPTORS, AND EXPOSURE PATHWAYS 88 3.2.1 T-117 Sediment Study Area 88 3.2.2 T-117 Upland Study Area 89 3.2.3 Adjacent Streets and Residential Yards Study Area Adjacent Streets 91 3.2.4 Adjacent Streets and Residential Yards Study Area Residential Yards 92 3.3 CONTAMINANTS OF CONCERN SELECTION PROCESS AND RESULTS 93 3.3.1 Sediment 95 3.3.2 Soil 100 3.3.3 Groundwater 106 3.3.4 RAA contaminants 114 3.3.5 Summary of streamlined risk assessment 115 4 Identification of Removal Action Scope, Goals, and Objectives 119 4.1 NTCRA SCOPE, GOALS, AND OBJECTIVES 119 4.2 REGULATORY REQUIREMENTS AND GUIDANCE 121 4.3 REMOVAL ACTION LEVELS 122 4.3.1 Development of sediment removal action levels 123 4.3.2 Development of soil removal action levels 129 4.3.3 Development of groundwater removal action levels 138 4.3.4 Summary of T-117 EAA removal action levels 144 4.4 REMOVAL BOUNDARY DETERMINATION 147 4.4.1 T-117 Sediment Study Area 147 4.4.2 T-117 Upland Study Area 147 4.4.3 Adjacent Streets and Residential Yards Study Area 148 5 Recontamination Assessment 150 5.1 OVERALL SOURCE CONTROL STRATEGY 150 5.2 POTENTIAL POST-NTCRA RECONTAMINATION SOURCES AND PATHWAYS 151 5.2.1 Erosion and transport of surface soil 157 5.2.2 Stormwater transport 161 5.2.3 Groundwater discharge 168 5.2.4 In-waterway sediment transport and deposition 170 5.2.5 Surface water transport within the LDW 172 5.2.6 Atmospheric deposition 172 5.3 OVERALL SUMMARY AND MONITORING RECOMMENDATIONS 177 Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page ii 6 Identification, Evaluation, and Screening of Technologies 181 6.1 SOIL AND SEDIMENT REMOVAL AND CONTAINMENT TECHNOLOGIES 183 6.1.1 Land-based technologies 184 6.1.2 Over-water technologies 184 6.2 MATERIAL TREATMENT AND DISPOSAL 187 6.3 SUMMARY OF RETAINED TECHNOLOGIES 195 7 Removal Action Alternatives 197 7.1 ALTERNATIVE 1: UPLAND SOIL EXCAVATION AND SEDIMENT EXCAVATION/ DREDGING COMBINED WITH CAPPING 201 7.1.1 Site preparation 202 7.1.2 Soil removal 206 7.1.3 Sediment removal and capping 218 7.1.4 Management of excavated and dredged materials 225 7.1.5 Completion of the removal action and coordination with future site uses 226 7.1.6 Summary of estimated costs 227 7.1.7 Evaluation of Alternative 1 227 7.2 ALTERNATIVE 2: UPLAND SOIL REMOVAL AND SEDIMENT EXCAVATION AND DREDGING 229 7.2.1 Site preparation 230 7.2.2 T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area removal activities 230 7.2.3 T-117 Sediment Study Area removal activities 230 7.2.4 Landfill disposal of excavated and dredged materials 231 7.2.5 Site completion and coordination with future site uses 231 7.2.6 Summary of estimated costs 232 7.2.7 Evaluation of Alternative 2 232 7.3 PROJECT COMPLETION OPTIONS 232 8 Comparative Analysis of Removal Action Alternatives 238 8.1 IMPLEMENTABILITY 238 8.1.1 Technical feasibility and availability 238 8.1.2 Administrative feasibility 240 8.1.3 Public involvement 241 8.2 EFFECTIVENESS 241 8.2.1 Overall protection of human health and the environment 241 8.2.2 Achievement of RAOs 241 8.2.3 Compliance with ARARs and other requirements 242 8.2.4 Reduction of toxicity, mobility, or volume through treatment 245 8.2.5 Short-term effectiveness and implementation risk 245 8.2.6 Long-term effectiveness and permanence 246 8.3 COST 248 Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page iii 8.4 SUMMARY OF COMPARATIVE ANALYSIS 249 9 Recommended Removal Action Alternative and Implementation 252 9.1 RECOMMENDED REMOVAL ACTION ALTERNATIVE 252 9.2 REMOVAL ACTION SEQUENCING AND SCHEDULE 253 9.2.1 Sequencing 253 9.2.2 Schedule 257 9.3 NTCRA WORK PLAN DEVELOPMENT 258 9.3.1 Health and Safety 258 9.3.2 Site Controls 259 9.3.3 Performance monitoring 259 9.4 ADDITIONAL INFORMATION NEEDS 260 9.4.1 Additional Streets and Yards Study Area information 262 9.4.2 Additional RAA information 262 9.4.3 Additional groundwater and geotechnical information 263 9.4.4 Refinement of excavation prisms 263 9.4.5 Site preparation and constraints 264 9.4.6 Coordination of final grade for site restoration transition 264 9.5 LONG-TERM OPERATION, MAINTENANCE, AND MONITORING PLAN 264 9.5.1 T-117 Sediment Study Area 267 9.5.2 T-117 Upland Study Area 267 9.5.3 Adjacent Streets and Residential Yards Study Area 268 9.5.4 Long-term OMMP summary 270 10 References 271 Appendices Appendix A. SOW Appendix B. Groundwater Appendix C. Data Tables Appendix D. Data Management Appendix E. COC Screening Appendix F. RAA Data Tables Appendix G. ARARs and Other Requirements to be Considered Appendix H. Risk-Based Disposal Application Appendix I. Combined Early Life Stage Adjustments and Soil Exposure Factors for Residential and Recreational PRG for cPAHsSoil Risk Calculation Supporting Details Appendix J. Cost Details Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page iv Appendix K. Detailed Technology Evaluation Appendix L. MIS Variance Appendix M. Dioxin Technical Workgroup Presentations (Note: Appendices are only provided on CD on inside back cover) List of Tables Table 2-1. Summary of 2009 T-117 Upland Study Area catch basin sampling results 17 Table 2-2. Summary of previous investigations at T-117 Early Action Area 51 Table 2-3. Summary of seep sampling field parameters at T-117 Early Action Area 75 Table 2-4. Summary of monitoring well parameters at T-117 Early Action Area 76 Table 3-1. Exposure pathways addressed by screening levels 94 Table 3-2. Sediment screening levels 95 Table 3-3. Sediment COPCs and COCs 99 Table 3-4. Soil screening levels 101 Table 3-5. Soil COPCs and COCs in the T-117 Upland Study Area 103 Table 3-6. Soil COPCs and COCs for Adjacent Streets 104 Table 3-7. Soil COPCs and COCs for Residential Yards 106 Table 3-8. Groundwater screening levels 110 Table 3-9. Groundwater COPCs and COCs 114 Table 3-10. Summary of exposure pathways and receptors identified in the streamlined risk assessment 116 Table 3-11. Summary of COCs identified in the streamlined risk assessment 117 Table 4-1. T-117 Sediment Study Area total risks for sediment removal action levels under the recreational scenario 125 Table 4-2. T-117 Upland Study Area soil removal action levels 131 Table 4-3. T-117 Upland Study Area total risks for soil removal action levels 135 Table 4-4. T-117 Adjacent Streets and Residential Yards Study Area total risks for soil removal action levels 138 Table 4-5. T-117 Upland Study Area groundwater removal action levels 141 Table 4-6. T-117 EAA sediment, soil, and groundwater removal action levels 145 Table 5-1. Concentrations of COCs identified at the Marina compared with T-117 Upland Study Area removal action levels 159 Table 5-2. Stormwater sampling results 164 Table 5-3. Hypothetical contribution of COCs to T-117 Sediment Study Area based on average atmospheric deposition flux rates 174 Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page v Table 5-4. Evaluation of post-removal recontamination risk from ongoing sources in the T-117 vicinity 177 Table 6-1. Review of candidate removal action technologies for the T-117 NTCRA 189 Table 6-2. Removal action technologies retained for the T-117 NTCRA 195 Table 7-1. Summary of site-wide removal action alternatives 199 Table 7-2. In-place volumes of soil and sediment to be removed and estimated sediment capping/backfilling volumes under Alternative 1 217 Table 7-3. Summary of estimated costs for Alternative 1 227 Table 7-4. In-place volumes of sediment to be removed and estimated sediment backfill volumes under Alternative 2 231 Table 7-5. Summary of estimated costs for Alternative 2 232 Table 8-1. Comparison of removal action alternatives relative to ARARs and other requirements TBC 243 Table 8-2. Comparison of costs for Alternatives 1 and 2 249 Table 8-3. Summary of comparative analysis 250 Table 9-1. Example NTCRA sequencing overview for primary construction tasks 254 Table 9-2. Supplementary information needed to support the removal action design 261 Table 9-3. Subjects and activities to be addressed in the T-117 OMMP 266 List of Figures Figure 1-1. Timeline of T-117 project history and regulatory milestones 3 Figure 2-1. Cross section locations 31 Figure 2-2. Geologic cross section A-A of the T-117 EAA 33 Figure 2-3. Geologic cross section B-B of the T-117 EAA 35 Figure 2-4. Geologic cross section C-C of the T-117 EAA 37 Figure 2-5. Geologic cross section D-D of the T-117 EAA 39 Figure 3-1. T-117 conceptual site model for current site conditions 85 Figure 4-1. Conceptual diagram of points of compliance for upland soil and sediment cleanup 128 Figure 4-2. Development of soil removal action levels 130 Figure 4-3. Development of groundwater cleanup levels 140 Figure 5-1. Overview of post-NTCRA potential sediment recontamination source areas and routes at the T-117 EAA 152 Figure 5-2. T-117 EAA possible post-NTCRA recontamination routes 155 Figure 6-1. Locations of zones within the shoreline and sediment 182 Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page vi Figure 7-1. Cross section E1 207 Figure 7-2. Cross section E2 209 Figure 7-3. Cross section E3 211 Figure 7-4. Cross section E4 213 Figure 7-5. Cross section E5 215 Figure 7-6. General sediment excavation and cap cross section 221 Figure 7-7. Upland completion options 235 Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page vii List of Maps All maps are included in a separate folio. Map 1-1. T-117 EAA site overview Map 2-1. T-117 EAA current and historical site features Map 2-2. T-117 EAA site drainage Map 2-3. Zoning designation and commercial and manufacturing activities in the vicinity of the T-117 EAA Map 2-4. Historical and current LDW configuration Map 2-5. Net groundwater flow direction, tidal efficiencies, and tidal lag times Map 2-6. Previous removal actions in the T-117 EAA Map 2-7. Sampling locations in the T-117 EAA and vicinity Map 2-8. T-117 Sediment Study Area total PCB concentrations in surface sediment Map 2-9 T-117 Sediment Study Area total PCB concentrations in subsurface sediment Map 2-10. T-117 Sediment Study Area sampling locations with full suite SMS analyses Map 2-11. T-117 Sediment Study Area dioxin/furan TEQs in surface sediment Map 2-12. T-117 Upland Study Area sampling subareas Map 2-13a. T-117 Upland Study Area total PCB concentrations in soil, 0-to-7-ft depth range Map 2-13b. T-117 Upland Study Area total PCB concentrations in soil, 7-to-15-ft depth range Map 2-13c. T-117 Upland Study Area total PCB concentrations in soil, >15-ft depth range Map 2-14. T-117 Upland Study Area Subarea A total PCB concentrations in soil Map 2-15. T-117 Upland Study Area Subarea B total PCB concentrations in soil Map 2-16. T-117 Upland Study Area Subarea C total PCB concentrations in soil Map 2-17. T-117 Upland Study Area Subarea D total PCB concentrations in soil Map 2-18. T-117 Upland Study Area Subarea E and F total PCB concentrations in soil Map 2-19a. T-117 Upland Study Area TPH concentrations in soil, 0-to-7-ft depth range Map 2-19b. T-117 Upland Study Area TPH concentrations in soil, 7-to-15-ft depth range Map 2-19c. T-117 Upland Study Area TPH concentrations in soil, >15-ft depth range Map 2-20. T-117 Upland Study Area Subarea A TPH concentrations in soil Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page ix Map 2-21. T-117 Upland Study Area Subarea B TPH concentrations in soil Map 2-22 T-117 Upland Study Area Subarea C TPH concentrations in soil Map 2-23. T-117 Upland Study Area Subarea D TPH concentrations in soil Map 2-24. T-117 Upland Study Area Subarea E and F TPH concentrations in soil Map 2-25. T-117 Upland Study Area cPAH TEQ concentrations in soil, 0-to-4-ft depth range Map 2-26. T-117 Upland Study Area cPAH TEQ concentrations in soil, 5-to->7-ft depth range Map 2-27. T-117 Upland Study Area arsenic concentrations in soil Map 2-28. T-117 Upland Study Area dioxin/furan TEQs in soil Map 2-29. Adjacent Streets total PCB concentrations in soil Map 2-30. Adjacent Streets total PCB concentrations in soil, 2008-2009 Map 2-31 Adjacent Streets and Residential Yards PCB concentrations, removed or superseded by MIS samples Map 2-32. Adjacent Streets TPH concentrations in soil Map 2-33. Adjacent Streets cPAH TEQs in soil Map 2-34. Adjacent Streets arsenic concentrations in soil Map 2-35. Adjacent Streets dioxin/furan TEQs in soil Map 2-36. Residential Yards PCB concentrations in soil Map 2-37. Residential Yards dioxin/furan TEQs in soil Map 2-38 Adjacent Streets and Residential Yards dioxin/furan concentrations, superseded by MIS samples Map 2-39. Sampling locations in Basin Oil Map 2-40. Sampling locations in the South Park Marina Map 3-1 T-117 EAA non-potability designation Map 4-1. T-117 EAA removal boundaries Map 4-2. T-117 EAA, soil interpolated total PCB concentrations, 0-to-7-ft depth range contours Map 4-3. T-117 EAA, soil interpolated total PCB concentrations, 7-to-15-ft depth range contours Map 4-4. T-117 EAA, soil interpolated total PCB concentrations, >15-ft depth range contours Map 4-5. T-117 EAA, soil interpolated TPH concentrations, 0-to-7-ft depth range contours Map 4-6. T-117 EAA, soil interpolated TPH concentrations, 7-to-15-ft depth range contours Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page x Map 4-7. T-117 EAA, soil interpolated TPH concentrations, >15-ft depth range contours Map 7-1. Proposed NTCRA, excavation for Alternative 12 Map 7-2. Proposed NTCRA, excavation for Alternative 2Removal Alternative 1: sediment excavation and cap Map 7-3 Comparison of Alternative 1 and 2 removal areas Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page xi Acronyms and Abbreviations AcronymCRONYM Definition AOC Administrative Order on Consent ARAR applicable or relevant and appropriate requirement ASAOC Administrative Settlement Agreement and Order on Consent AST aboveground storage tank ATSDR Agency for Toxic Substances and Disease Registry Basin Oil Basin Oil Company, Inc. BBP butyl benzyl phthalate BEHP bis(2-ethylhexyl) phthalate bgs below ground surface BMP best management practice BTEX benzene, toluene, ethylbenzene, and xylene Boeing The Boeing Company CCC criteria continuous concentration CD compact disk Comprehensive Environmental Response, Compensation, and Liability CERCLA Act (Superfund) CFR Code of Federal Regulations cfs cubic feet per second City City of Seattle CMC criteria maximum concentration COC contaminant of concern COPC contaminant of potential concern County King County cPAH carcinogenic polycyclic aromatic hydrocarbon CSGWPP Comprehensive State Ground Water Protection Program CSL cleanup screening level CSM conceptual site model CSO combined sewer overflow CSS combined sewer system CUL cleanup level cy cubic yard DDD dichlorodiphenyldichloroethane DDE dichlorodiphenyldichloroethylene DDT dichlorodiphenyltrichloroethane DOF Dalton, Olmsted & Fuglevand, Inc. DPD Department of Planning and Development DU decision unit Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page xiii AcronymCRONYM Definition dw dry weight EAA early action area Ecology Washington State Department of Ecology EE/CA engineering evaluation/cost analysis EFH essential fish habitat EPA US Environmental Protection Agency FRTR Federal Remediation Technologies Roundtable FS feasibility study FSP field sampling plan HHRA human health risk assessment HPAH high-molecular-weight polycyclic aromatic hydrocarbon HQ hazard quotient Integral Integral Consulting, Inc. KCBOH King County Board of Health KCCWD1 King County Commercial Waterway District No. 1 LDW Lower Duwamish Waterway LDWG Lower Duwamish Waterway Group LNAPL light non-aqueous-phase liquid LPAH low-molecular-weight polycyclic aromatic hydrocarbon Malarkey Malarkey Asphalt Company Marina South Park Marina MCL maximum contaminant level MIS multi-increment sampling MLLW mean lower low water MTCA Model Toxics Control Act NMFS National Marine Fisheries Service NOAA National Oceanic and Atmospheric Administration NPDES National Pollutant Discharge Elimination System NPL National Priorities List NRDA natural resource damage assessment NTCRA non-time-critical removal action O&M operation and maintenance OC organic carbon OMMP operation, maintenance, and monitoring plan ORP oxidation-reduction potential OSWER Office of Solid Waste and Emergency Response PAH polycyclic aromatic hydrocarbon RBTC risk-based threshold concentration PCB polychlorinated biphenyl PCE tetrachloroethylenes Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page xiv AcronymCRONYM Definition Port Port of Seattle PQL practical quantitation limit PRG preliminary remediation goal PSDDA Puget Sound Dredged Disposal Analysis QAPP quality assurance project plan QA/QC quality assurance/quality control RAA recontamination assessment area RAL remedial action level RAO removal action objective RBTC risk-based threshold concentration RCRA Resource Conservation and Recovery Act RI remedial investigation RM river mile ROD Record of Decision ROW right-of-way RvAL removal action level SAIC Science Applications International Corporation SCAP source control action plan SCL Seattle City Light SCWG Source Control Work Group SL screening level SMC Seattle Municipal Code SMS Washington State Sediment Management Standards SOW statement of work SPCC South Park Community Center SPU Seattle Public Utilities SQS sediment quality standards STAR sediment transport analysis report STM sediment transport model SVOC semivolatile organic compound T-117 Terminal 117 TBT tributyltin TCDD tetrachlorodibenzo-p-dioxin TCLP toxicity characteristic leaching procedure TCRA time-critical removal action TEE terrestrial ecological evaluation TEF toxic equivalency factor TEQ toxic equivalent TOC total organic carbon TPH total petroleum hydrocarbons Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page xv AcronymCRONYM Definition TPH-D diesel-range total petroleum hydrocarbons TPH-O lube oil-range total petroleum hydrocarbons TSCA Toxic Substances Control Act UCL upper confidence limit on the mean USACE US Army Corps of Engineers USFWS US Fish and Wildlife Service UST underground storage tank VOC volatile organic compound WAC Washington Administrative Code WSDOH Washington State Department of Health Windward Windward Environmental LLC Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page xvi 1 Introduction Terminal 117 (T-117) is a site within the Lower Duwamish Waterway (LDW) Superfund site that was selected for early action in 2003 to address polychlorinated biphenyl (PCB) contamination in sediment. An upland portion of T-117 was historically used for the manufacture of asphalt products, as well as other activities associated with former tenants. Asphalt manufacturing operations at the site included the use of recycled oils, some of which contained PCBs, and these oils are believed to be a source of contaminants released to the surrounding soil and sediment. In 2005, the Port of Seattle (Port) and the City of Seattle (City) prepared an engineering evaluation/cost analysis (EE/CA) for a non-time-critical removal action (NTCRA) for the sediment and adjacent shoreline bank area, which was submitted to the US Environmental Protection Agency (EPA). EPA approved the 2005 EE/CA (Windward et al. 2005c) for the T-117 Early Action Area (EAA) sediment and adjacent bank and issued an action memorandum (EPA 2006a), which set forth the implementation of the NTCRA. At that time, it was assumed that only minor revisions to the upland side of the sediment removal action boundary would be needed. However, in 2006, additional PCB contamination was discovered in the T-117 upland property, the extent of which was broader than originally anticipated. This resulted in an increased scope for the NTCRA. In addition, in 2004-2005, PCBs were discovered in the streets adjacent to the T-117 upland property and removed from two residential yards.;, and in 2008, PCBs and dioxins and furans were discovered in residential yards near the T-117 EAA. In March of 2007, the Washington State Department of Ecology (Ecology) notified EPA that it supported incorporating the work proposed by the City for Dallas Avenue S into EPA's T-117 NTCRA (Ecology 2007). Thus, the T-117 EAA was expanded by EPA to include three areas, hereafter referred to as the T-117 Sediment Study Area, the T-117 Upland Study Area, and the Adjacent Streets and Residential Yards Study Area. In 2008, LDW source control samples collected in 2004-2005 were evaluated for dioxins and furans, and concentrations were determined to be above the Model Toxics Control Act (MTCA) Method B cleanup level (CUL) at two locations near T-117. EPA ordered additional analysis for PCBs and dioxins and furans in 2008, and both contaminants were discovered above the MTCA Method B CUL in streets, rights- of- way (ROWs), and residential yards. As a result, EPA directed the Adjacent Streets portion of the T-117 EAA to be expanded to include the area bounded by Dallas Avenue S to the north and east, 14th Avenue S to west, and S Donovan Street to the south (EPA 2009c). This area is now referred to as the Adjacent Streets and Residential Yards Study Area. The scope of the T-117 EE/CA includes the evaluation of removal action alternatives for all three of the T-117 study areas. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 1 The scope of this EE/CA is set forth in the Terminal 117 Early Action Area Work Plan for Revised Engineering Evaluation/Cost Analysis (Windward et al. 2008), hereafter referred to as the EE/CA Work Plan. This EE/CA is being prepared by the Port and the City pursuant to an Administrative Settlement Agreement and Order on Consent (ASAOC) with EPA (Docket No.10-2006-0103, December 22, 2005 (EPA 2005b)) and in accordance with Amendment No. 1 to the statement of work (SOW) dated September 28, 2007 (EPA 2007c) (Appendix A). The SOW also required an assessment of the potential for recontamination of the T-117 EAA by the adjoining Basin Oil Company, Inc. (Basin Oil), property and South Park Marina (Marina), collectively referred to as the recontamination assessment areas (RAAs). Map 1-1 shows the T-117 EAA and the RAAs. An evaluation of the RAAs is included in this EE/CA, which is necessary to ensure the long-term permanence of the selected removal alternative. In addition, the scope of this EE/CA complies with the requirements set forth in EPA's Guidance on Conducting Non-Time-Critical Removal Actions Under CERCLA (1993), including a comprehensive compilation of existing site data to support the identification and analysis of contaminants of concern (COCs), site risks, and the removal alternatives necessary to address those contaminants and associated risks. EPA has specifically requested that the EE/CA include removal action alternatives that are compatible with the anticipated future unrestricted land use (EPA 2007b) (Appendix A). The presentation of removal action alternatives includes a discussion of different ways in which the removal action can be completed in order to meet EPA's future land use request. Removal action technologies are similar to those presented in the 2005 EE/CA (Windward et al. 2005c) and the 2008 EE/CA Work Plan (Windward et al. 2008) and are further developed and refined in this EE/CA. The overall goal of the T-117 EAA NTCRA is to significantly reduce the exposure of ecological and human receptors to sediment and soil contamination and thereby reduce or eliminate adverse effects on resources in the EAA. The NTCRA will also reduce risks to human health by removing or isolating bioaccumulative and toxic chemicals that are present in sediment and soil at the T-117 EAA (EPA 2005c). In addition, the removal of contaminated soil will reduce or eliminate groundwater contamination. 1.1 CERCLA PROJECT PROGRESSION This section summarizes the history of the LDW as a Superfund site and the identification of the T-117 as an EAA within the LDW. T-117 has been investigated by both state and federal agencies prior to the LDW Superfund listing. Additional details on the regulatory history prior to the LDW Superfund designation are presented in Sections 2.1.2 and 2.2, respectively. A timeline showing project history and regulatory milestones is presented in Figure 1-1. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 2 Slipsheet (11 x 17) Figure 1-1. Timeline of T-117 project history and regulatory milestones Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 3 1.1.1 Lower Duwamish Waterway and early action areas The T-117 EAA is within the LDW Superfund site. The LDW was added to EPA's National Priorities List (NPL) defined under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), also known as Superfund, on September 13, 2001. The Phase 1 remedial investigation (RI) report for the LDW (Windward 2003a) presented a summary of available data for the waterway. One of the primary objectives of the Phase 1 RI was to identify candidate areas within the LDW for early removal action. The Port, the City, King County (County), and The Boeing Company (Boeing), working together as the Lower Duwamish Waterway Group (LDWG), prepared a technical memorandum (Windward 2003b) that recommended seven areas, one of which was T-117, to EPA and the Washington State Department of Ecology (Ecology) for early removal action. In 2003, EPA required that T-117 be investigated as an EAA, primarily because of the high concentrations of PCBs and the potential for those PCBs to contaminate LDW sediment (EPA 2005b). 1.1.2 Initial early action area investigations and 2005 EE/CA Since T-117 was selected as an EAA, the Port and the City have conducted a series of environmental investigations to further characterize environmental conditions in the Sediment Study Area, identified a removal action boundary, and investigated potential sources of contamination. The results of these efforts have included a summary of existing information and data gaps report (Windward et al. 2003), several data reports (Windward et al. 2005b, d, e), and the 2005 EE/CA (Windward et al. 2005c). These investigations (and the resulting reports) for the T-117 EAA were conducted under the existing LDW Administrative Order on Consent (AOC) (EPA 2003) signed by all of the LDWG members, as well as by EPA and Ecology. Although all four members of LDWG are responsible for the LDW RI (Windward 2009), work at the T-117 EAA is conducted by only the Port and the City. After the approval of the 2005 EE/CA (Windward et al. 2005c) on July 22, 2005, EPA issued a removal action memorandum (EPA 2005a) to implement the NTCRA design and removal activities. The removal action memorandum requested further characterization of PCB contamination in the northern portion of the bank necessary to finalize the removal action boundary prior to NTCRA implementation. The additional bank characterization sampling resulted in the discovery of higher-than-expected PCB concentrations in the bank at the northern part of the T-117 EAA. This led EPA to require further sampling to delineate the extent of PCBs in the upland soil. An ASAOC (CERCLA 10-2006-0072) (EPA 2005c) was issued solely to the Port on October 17, 2005, for an additional T-117 upland soil investigation to determine the nature and extent of upland PCB soil contamination. In an effort to continue moving forward on NTCRA activities, on December 22, 2005, an ASAOC (EPA 2005b) was issued jointly to the Port and the City with a SOW for the NTCRA design and removal. However, in January Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 5 2006, additional site characterization investigations conducted by the Port found high concentrations of PCBs in soil (Windward and DOF 2006). These data concentrations prompted a time-critical removal action (TCRA) to remove contaminated soil from specific areas within the T-117 Upland Study Area prior to conducting the NTCRA, which postponed the joint Port and City NTCRA activities. 1.1.3 2006 time-critical removal action At the direction of EPA, the Port implemented the TCRA for the T-117 Upland Study Area to remove upland source materialcontaminated soil that could potentially recontaminate the sediment and affect the success of the planned NTCRA for the Sediment Study Area. A TCRA memorandum (EPA 2006a) to address risks posed by the upland soil contamination was issued by EPA on June 15, 2006. EPA concluded that the scope of the TCRA would be limited to those areas of T-117 with the highest documented concentrations of PCBs in soil, as well as a limited area near the bank with exposed contaminated soil (i.e., an unpaved area), and that the rest of the upland contamination would be more efficiently addressed as in the T-117 EAA NTCRA. The SOW (EPA 2006b) for the implementation of the TCRA to address the most contaminated areas of the T-117 Upland Study Area was issued to the Port on August 11, 2006. The Port completed the TCRA in November 2006 (RETEC 2007b). The SOW required the implementation of the post-TCRA site operation and maintenance (O&M) program, which is currently ongoing (RETEC 2007a). Semi-annual O&M reports are submitted to EPA. Details, such as excavation volumes and depths, of the 2006 TCRA removal activities are discussed in Section 2.2.3. 1.1.4 Inclusion of the Adjacent Streets In 2007, the City requested that Ecology support the inclusion of the Adjacent Streets and ROWs in EPA's NTCRA with the intention that the temporary measures implemented as part oft the City's previous independent cleanup actions (i.e., temporary asphalt and gravel on roads and ROWs and surface water collection system routed to Baker tanks) would be replaced and longer needed after implementation of the NTCRA. 1.1.45 Dioxin investigations and PCB boundary refinement The City's source-tracing program for the LDW (Herrera 2004) included the analysis of 11 samples, including two 2 samples collected near T-117, for dioxins and furans. The two samples included one street dust (i.e., fine soil accumulated on street surfaces and shoulders) sample collected at the intersection of Dallas Avenue S and 16th Avenue S (within the area now designated as the Adjacent Streets portion of the T--117 EAA) and a sample collected from a settling tank (later replaced by an oil-water separator) located on the Basin Oil property. The LDW source-tracing samples were analyzed for Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 6 a suite of chemicals. Dioxin congener concentrations from this sampling program were used to calculate toxic equivalents (TEQs),1 concentrations, which were reviewed by the City in 2008 (Integral 2008b). The dioxin/furan TEQs for the street dust and the settling tank samples were 90.5 ng/kg and 15.2 ng/kg, respectively. The street dust sample dioxin/furan TEQ was more than twice the maximum TEQ of the other 11 samples and was found in an area where PCB concentrations were above the MTCA Method B CUL. Because these data are not related to the T-117 EAA, their significance is uncertain.two source-tracing samples, it is unclear if these samples reflect isolated areas with higher levels of dioxin/furan TEQs. As a result of these findings, the City proposed an additional investigation (Integral 2008a) of residential yards to examine the presence of dioxins and furans in the vicinity of the street dust sample, which was to include the collection of samples in several yards and from borings in the streets. EPA requested that additional investigations be conducted in all three T-117 EAA study areas. These investigations were conducted in 2008 and 2009 (Windward and Integral 2009; Integral 2009). The 2008 investigation resulted in detections of dioxins and furans, and PCBs in sediment, upland soil, streets, parking strips, and yards. These results led to EPA's request for additional sampling in yards and the Adjacent Streets using multi-increment sampling (MIS) techniques in order to refine the boundaries and determine mean exposure concentrations in the yards. The 2008-2009 MIS soil sampling effort resulted in the detection of PCB concentrations above 1 mg/kg in portions of the Adjacent Street and in some Residential Yards. Dioxin/furan TEQs exceeded the MTCA CUL of 11 ng/kg at many locations and ranged from 0.495 to 84.0 ng/kg. One TEQ of 395 ng/kg was considered to be an outlier (see Section 2.3.3). As a result of these investigations, EPA directed that the Adjacent Streets portion of the T-117 EAA be expanded to include the area bounded by Dallas Avenue S to the north and east, 14th Avenue S to west, and S Donovan Street to the south (EPA 2009c). As shown on Map 1-1, this area is now referred to as the Adjacent Streets and Residential Yards Study Area. 1.1.56 Expanded T-117 EAA and the revised EE/CA This EE/CA is being prepared in accordance with the EE/CA Work Plan (Windward et al. 2008) and SOW Amendment 1 (EPA 2007c), the latter replacing in its entirety the SOW appended to the NTCRA ASAOC issued on December 22, 2005. SOW Amendment 1, issued on September 28, 2007, states that the revised EE/CA will include the information presented in the previous EE/CA (Windward et al. 2005c) and will also include new information that has been generated since the 2005 EE/CA. Such information includes the following datasets, which are discussed in greater detail in Sections 2.2 and 2.3. 1 Dioxin/furan TEQs were calculated in accordance with Ecology's calculation guidance (WAC 173-340- 900, Table 708-1). Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 7 Data collected by the Port in support of its investigation of the T-117 Sediment Study Area Data collected by the Port in support of its investigation and removal action activities within the T-117 Upland Study Area Pertinent information from the river-wide LDW RI/feasibility study (FS) Data collected by the City in support of its investigation and independent cleanup action activities within the Adjacent Streets and Residential Yards Study Area Data collected by Ecology and EPA in support of their dioxin and furan investigation within the Adjacent Streets and Residential Yards Study Area Data collected as part of the T-117 data gaps assessment, including groundwater monitoring activities set forth in the SOW Data collected by Ecology and EPA in conjunction with past and ongoing investigation and cleanup actions at Basin Oil Data collected by Ecology as part of its investigation of the Marina This EE/CA includes an identification and analysis of removal action technologies and alternatives for the expanded T-117 EAA as well as previously analyzed sediment removal alternatives, taking into consideration all new information from the abovenoted sources. Following the completion of this EE/CA, EPA will issue an amended action memorandum for the T-117 EAA NTCRA, which will replace the action memorandum issued on July 22, 2005. 1.2 EE/CA ORGANIZATION This EE/CA is organized in accordance with SOW Amendment 1 (EPA 2007c), which is an appendix of the ASAOC (EPA 2005c). The contents and EE/CA approach are detailed in the approved EE/CA Work Plan (Windward et al. 2008). The remaining sections of this EE/CA are organized as follows: Section 2, Site Characterization Presents a summary of historical operations, previous investigation and removal actions, current site conditions, land use, geology, and hydrogeology. This section also discusses the nature and extent of contamination based on sediment, soil, and groundwater for the T-117 EAA and the RAAs. Section 3, Streamlined Risk Assessment Presents the conceptual site model (CSM), which shows the current and potential sources, transport mechanisms and exposure pathways to potential receptors. The contaminants of potential concern (COPCs) presented in the EE/CA Work Plan (Windward et al. 2008) are further evaluated, and specific contaminants were selected as COCs through a streamlined risk assessment. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 8 Section 4, Identification of Removal Action Scope, Goals, and Objectives Presents the development of removal action levels (RvALs) for sediment and soil necessary to address the removal action goals and objectives. These goals include contaminant removal sufficient to allow for a broad range of final site uses at T-117, including possible upland and aquatic habitat. This section also presents the removal boundaries for each of the T-117 EAA areas. Section 5, Recontamination Assessment Provides an overview of the source control strategy, identifies potential recontamination sources and pathways, and evaluates the potential for the pathways to recontaminate the post-NTCRA site. This section also describes the results of the recontamination assessments for the Basin Oil property and Marina, which were initially presented in the EE/CA Work Plan (Windward et al. 2008), and has been updated based on identified data needs and recent investigations by Ecology. Section 6, Identification, Evaluatioin, and Screening of Removal Action Technologies Identifies, discusses, and screens the potentially applicable removal action technologies for soil and sediment removal, treatment, and offsite disposal. Technologies retained after screening are intended for use as part of the assembled removal action alternatives presented in Section 7. Section 7, Description and Analysis of Removal Action Alternatives Presents the removal action alternatives and describes how they will be applied in each removal area of the EAA. Each alternative is also discussed in terms of its implementability, effectiveness, and cost to facilitate the comparative analysis in Section 8. Section 8. Comparative Analysis of Removal Action Alternatives Provides a comparative discussion of the removal alternatives based on the CERCLA criteria of effectiveness, implementability, and cost. Section 9. Recommended Removal Action Alternative and Implementation Describes and presents the rational for the recommended alternative for the NTCRA. Presents the preliminary removal action sequencing concepts, short- term and long-term monitoring objectives, and general a description of NTCRA activities to be conducted during design and during and after construction. Section 9 includes a description of the long-term operation, maintenance, and monitoring plan (OMMP) that will be developed and implemented to ensure the long-term performance of the selected removal action alternative. The section also includes a discussion of the data gaps that will be needed prior to the removal action. Section 10, References Includes references for published documents and other sources cited in this EE/CA. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 9 The following appendices support the text: Appendix A. SOW and Reasonably Anticipated Future Land Use Letter Appendix B. Groundwater Appendix C. Data Tables Appendix D. Data Management Appendix E. COC Screening Appendix F. RAA Data Summary Tables Appendix G. ARARsS and Other Requirements to be Considered Appendix H. Risk-Based Disposal Application Appendix I. Combined Early Life Stage Adjustments and Soil Exposure Factors for Residential and Recreational PRG for cPAHsSoil Risk Calculation Supporting Details Appendix J. Cost Details Appendix K. Detailed Technology Evaluation Appendix L. MIS Variance Appendix M. Dioxin Technical Workgroup Presentations The appendices are provided only on a compact disk, (CD) which is located on the inside back cover. The CD also includes a copy of this report and the figure and map folio. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 10 2 Site Characterization This section presents a summary of the available environmental, physical, and ecological information relevant to the T-117 EAA. The section also includes a description of the historical activities, regulatory history, and current site features. The current site uses and activities occurring in the vicinity are also described. There is also discussion ofon the LDW and the geology inof this area. Finally, the previous environmental investigation and clean-up actions in the T-117 EAA and RAAs are summarized. 2.1 SITE DESCRIPTION 2.1.1 Location and characteristics The T-117 EAA is situated on the west bank of the LDW, between approximately River Mile (RM) 3.5 and RM 3.7 (relative to the southern tip of Harbor Island) (Map 1-1). The EAA is located approximately 6 miles south of the Seattle downtown area and is across the LDW from Boeing Plant 2 and Jorgensen Forge, which together form another EAA. The T-117 Upland Study Area is located within a narrow strip of unincorporated King County that lies between the LDW to the east and the South Park neighborhood of Seattle to the west. The Port's T-117 property, which includes the T-- 117 Upland Study Area, is located at 8700 Dallas Avenue S and is immediately south of the 16th Avenue S bridge (also known as the South Park Bridge) (Map 1-1). The T-117 EAA is characterized by gently sloping intertidal mudflat habitat, a steep vegetated riprap bank, and a relatively flat adjacent upland area. The T-117 EAA encompasses approximately 15.2 acres and consists of the three defined areas: the Sediment Study Area within the LDW, the T-117 Upland Study Area (Port-owned T-- 117 property), and the Adjacent Streets (City rights-of-way [ROWs]) and Residential Yards Study Area. Each area of the T-117 EAA is described in further detail in the subsections that follow. The T-117 EAA is also adjacent to the Marina and Basin Oil properties, which are being evaluated as potential sources of recontamination to the T-117 EAA. These areas are also shown on Map 1-1 and are discussed in detail in Section 2.3.4. 2.1.1.1 Sediment Study Area The T-117 Sediment Study Area is the aquatic portion of the T-117 EAA. Located within the LDW (Map 1-1), the study area is approximately 1.4 acres in size and consists primarily of intertidal sediment with some subtidal sediment. The study area extends from the top of the shoreline bank, at an elevation of approximately+13.8 ft mean lower low water (MLLW), into the LDW (60 to 80 ft), at an elevation between 0 and -5 ft MLLW. This area is bordered by the LDW to the north and south, the LDW navigation channel to the east, and the T-117 Upland Study Area to the west. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 11 2.1.1.2 T-117 Upland Study Area The T-117 Upland Study Area consists of the Port's T-117 upland property located between the T-117 Sediment Study Area and the Adjacent Streets and Residential Yards Study Area (Map 1-1). This property, which includes the former Malarkey Asphalt Company (Malarkey) Plant property, is located at 8700 Dallas Avenue S. In 1963, the Port accepted the assets of the King County Commercial Waterway District No. 1 (KCCWD1) (Map 2-1), which included limited rights in a 500-ft-wide strip of upland property along the T-117 shoreline. ROW acquired to create a portion of the LDW. In 20001999, the Port acquired two inland parcels that included the former Malarkey property between the shoreline KCCWD1 parcel and Dallas Avenue S. These properties were consolidated to form the present-day footprint of T-117, which encompasses approximately 3.3 acres. This area is relatively flat with an elevation that ranges from approximately +13.8 ft MLLW at the top of the bank to approximately +21 ft MLLW along the property boundaries at Dallas Avenue S and the Marina. The T-117 Upland Study Area is bordered by the Marina to the north, Boeing South Park to the south, Dallas Avenue S to the west, and the T-117 Sediment Study Area and the LDW to the east. 2.1.1.3 Adjacent Streets and Residential Yards Study Area The Adjacent Streets and Residential Yards Study Area consists of two subareas: the Adjacent Streets and the Residential Yards. The Adjacent Streets portion is the street and ROW areas bounded by Dallas Avenue S, S Donovan Street, and 14th Avenue S. These streets and ROWs are relatively flat with the exception of S Donovan Street. The lanes of this street are separated by a steep bank and the southern-most lane is elevated relative to other streets in the area. The Adjacent Streets are bordered by the T-117 Upland Study Area to the east and the Marina to the north. The Adjacent Streets also surround, but do not include, the former Basin Oil property and Residential Yards within the bounding streets mentioned above. The Residential Yards consist of the residential properties within the boundaries of Dallas Avenue S, S Donovan Street, and 14th Avenue S. These yards are relatively flat with some local minor variations in topography. 2.1.2 Historical activities 2.1.2.1 T-117 operations The Duwamish Manufacturing Company began manufacturing asphalt roofing materials at T-117 around 1937 and continued until 1978 at a location that generally corresponds to the western half of the T-117 Upland Study Area (URS 1994). The business and property were sold in 1978, when it became known as the Malarkey Asphalt Company. Asphalt roofing materials manufacturing continued until 1993. Since that time, several environmental site investigations werehad been conducted until the asphalt plant was decommissioned in 1997. During the Duwamish Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 12 Manufacturing Company's operation of the asphalt manufacturing facility from the late 1960s through the mid 1970s, used oils, some of which contained PCBs, were used as fuel for the asphalt manufacturing process (URS 1994). Some used oils came from Seattle City Light. Features formerly associated with the asphalt plant (Map 2-1) but no longer present at the site include underground and aboveground storage tanks (USTs and ASTs) and associated piping, reaction tanks, sumps, a diesel fuel dispenser, a hot oil heater and associated shed, transfer pumps and pipes, warehouses at the east side of the plant area, a drum storage shed, and a partially buried railroad tank car (URS 1994). A former ponding area was located just inland of the top of the shoreline bank (Map 2-1) and was reportedly used during site operations for retaining non-contact cooling water (Hart Crowser 1992; URS 1994). This area was later determined to merely be a depression in the unpaved area of the site where stormwater collected and vehicles drove through the property. The ponding area was the lowest point on the T-117 Upland Study Area and also collected all water that flowed across the site, including non-contact cooling water from the main manufacturing area. Periodic overflow from the former ponding area to the LDW was noted during extended rainy periods (EMCON 1996). The former ponding area was located within the former KCCWD1 ROW (EMCON 1996) and was subsequently excavated as part of a contaminated soil TCRA in 1999 and backfilled (Onsite 2000a) (see Section 2.2.2). From 1989 to as late as 1995, Basin Oil leased a 10,000-gal. horizontal tank from Malarkey within the plant area for storing and processing used oil (EPA 1995). After the asphalt plant was decommissioned in 1997, portions of the property were occupied by Evergreen West Wholesale (a lumber wholesaler) for untreated lumber storage and loading (Windward et al. 2003). From 2003 to 2004, through a lease with the Port, Basin Oil also used a portion of the interior of the south building on the T-117 property for storage and oil filter processing (Windward et al. 2003). In 20001999, the Port acquired the asphalt plant parcels and related buildings located between the shoreline ROW parcel and Dallas Avenue S. This acquisition was part of an agreement in which the Port would conduct the 1999 TCRA in exchange for the parcels. The Port consolidated the asphalt plant parcels with the KCCWD1 parcel to form the presentday T-117 Upland Study Area. After the Port acquired the property, Port Construction Services used the outdoor area near the small office/carport for the storage of miscellaneous materials. International Inspection, a provider of non-destructive testing services, formerly leased the north building and the small office/carport. Second Use Building Materials, Inc., a recycling business that obtains reusable building materials from demolition projects for resale to the public, leased the south building for inventory storage. The T-117 Upland Study Area has been vacant since February 2007. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 13 2.1.2.2 Adjacent Streets and Residential Yards Study Area Aerial photographs show that the current street configuration in the South Park area was largely established as early as 1936. Available records indicate that S Cloverdale Street, between 14th Avenue S and 16th Avenue S, was paved or resurfaced with asphalt in 1947 (Allwine 2005). Other streets in the area (Dallas Avenue S, S Donovan Street, 16th Avenue S, and 17th Avenue S) remained unpaved until the mid-1970s or later, which extends into the period when used oils were handled by the Duwamish Manufacturing Company and Basin Oil (described below). Prior to an independent cleanup action conducted by Seattle Public Utilities (SPU) in 2004-2005 (Section 2.2.4), the streets surrounding Basin Oil had no formal stormwater collection system within the Adjacent Streets portion of the EAA. Businesses historically located within the neighborhood adjacent to T-117 included Basin Oil, the Marina, Seattle Chocolate Company, Allied Bolt Company, and Fasteners, Inc; these businesses are briefly described below. Basin Oil and the Marina are further evaluated as RAAs, and additional site information and the results of environmental investigations for these properties are presented in Section 2.4. Until 2007, the Basin Oil site was occupied by the Basin Oil Company, which operated as a collector, transporter, and marketer of used oil. Used oil was delivered to the facility by tank trucks and stored in tanks prior to treatment and recycling. The property was also the former site of operations for other affiliated companies including Northwest Antifreeze Service, Frontwater Service, and Vintage Oil Inc., all of which were handlers of used oil or antifreeze products. Basin Tank and Environmental Services, Inc., also operated on the site, but that company closed in January 2002. According to Ecology records (Ecology 2004b), Basin Oil began operating at the site in 1987. Prior to development as an industrial facility, the site included residential parcels and a single-family residential structure. The site is currently inactive, and cleanup actions by the owner have been conducted since the plant closure in 2007 (EPA 2007a). There is little information regarding historical activities at the Marina (SAIC 2007b). A portion of the land that currently comprises the Marina was a mobile home park. Boat transport and engineering operations have also been conducted in the boat yard. A&B Barrel, a barrel refurbishing and cleaning operation, was located at the site in the 1950s (Windward et al. 2003). Former occupants of the central portion of the site reportedly included North Star Trading Company (1980 to 1981), Evergreen Boat Transport (1985 to 1999), R.P. Boatbuilding (dates unknown), and Dekker Engineering (1995 to 1999). Seattle Chocolate Company, Allied Bolt Company, and Fasteners, Inc., occupied the same property (located at 8619 and 8620 17th Avenue S) at various times; Caf Umbria currently occupies the property. The City conducted a site history assessment of this property in general accordance with EPA standard practice (40 Code of Federal Regulations [CFR] 312). County records indicate the building was constructed in 1971 and first occupied in 1979. City records document a connection made to the City sewer Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 14 in 1979 (at which time Allied Bolt Company was a tenant). The Allied Bolt Company and Fasteners, Inc., were classified as small-quantity generators, although and no violations were noted in association with their operations. Chemicals potentially associated with operations at the Allied Bolt Company and Fasteners, Inc., may have included volatile organic compounds (VOCs) and metals. A records search (King County 2008; Ecology 2008a; City of Seattle 2008; Ecology 2008b) did not indicate that any COPCs were associated with the Seattle Chocolate Company. 2.1.3 Current site features 2.1.3.1 Upland structures and infrastructure Since the asphalt plant was decommissioned in 1997, the only aboveground structures that remain on the T-117 Upland Study Area are the north and south buildings, the small office/carport inside the north gate, and the truck scale at the west side of the property. The remainder of the T-117 Upland Study Area is covered with asphalt or concrete pavement with the exception of a vegetated drainage ditch along the southern boundary. Asphalt plant structures that remain at T-117 beneath the ground surface include the three closed-in-place USTs; the decommissioned large-diameter industrial water supply well; concrete foundations associated with the former warehouse structures, reaction tanks, cooling water sump, and tank pads, and underground utility corridor; and a shallow, concrete-lined ditch that has subsequently been cleaned out and backfilled with controlled density fill (Windward and Onsite 2004). Some small-diameter remnant buried piping associated with the former plant may also be present, although most of this piping was removed during plant demolition and the subsequent cleanout of the concrete-lined utility corridor. The property is fenced, and gates are locked to control public access. The buildings on T-117 are supplied with potable water from the City public water supply system. The north building and the office/carport building discharge grey water and sewage to the septic system onsite. These features are shown on Map 2-1. An overhead power line (Seattle City Light's Dallas Avenue Crossing) was temporarily removed in 2004. This overhead power line passed through the Adjacent Streets along an existing easement across the T-117 Upland Study Area and across the T-117 Sediment Study Area. The current 12-ft-wide easement across the upland property is shown on Map 2-1, and the historical lines are visible on Map 1-1; these lines traversed the T-117 Upland Study Area, in the vicinity of the Dallas Avenue S and 17th Avenue S intersection, and extended east across T-117 and the LDW to a location near the southwest corner of the Boeing Plant 2 property. The overhead power line is scheduled for reconstruction following completion of the NTCRA. The Adjacent Streets are paved, with gravel surfacing in some shoulder areas (along Dallas Avenue S, and 16th Avenue S). Sidewalks, with grass buffer strips and occasional trees, are present along sections of Dallas Avenue S, 16th Avenue S, and 17th Avenue S (Map 2-1). Overhead power lines and underground utilities (e.g., gas, Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 15 water, telephone, combined sewer system [CSS]) exist throughout the area. Stormwater in the area east of 16th Avenue S drains to the CSS. A temporary stormwater collection system was installed and pavement improvements were completed within portions of the Adjacent Streets as part of the City's independent cleanup actions (see Section 2.2.4). 2.1.3.2 Offshore debris and structures Waste materials that may be associated with historical upland operations are present in the riprap of the shoreline berm, on the vegetated berm crest, and in the drainage ditch at the south side of T-117 Upland Study Area. These waste materials include 55-gal. drums, semi-soft and hardened asphalt and asphalt roofing materials. Weathered chunks of asphalt are also present on the intertidal mudflat. Photographs and maps of the locations of these waste materials are included in the 2004 data report (Windward et al. 2004). A deteriorating bulkhead located offshore of the north half of the T-117 EAA can be observed today at the base of the riprap and can also be seen in a 1946 aerial photograph (Windward et al. 2003) as a row of pilings in the intertidal area. Also, a row of treated pilings and a log boom used to divert floating debris away from the Marina is located in the intertidal area near the boundary with the Marina. 2.1.3.3 Drainage and outfalls Map 2-2 shows the outfalls, sewer and storm drain lines, and catch basins associated with the drainage in the T-117 EAA and vicinity. Two storm drain outfalls located along the T-117 shoreline bank are owned by the Port and discharge runoff from stormwater conveyances located on the T-117 Upland Study Area. These two outfalls discharge directly to the LDW and T-117 EAA Sediment Study Area. Threewo storm drain outfalls are located to the north of T-117, located along the shoreline bank of the Marina and , discharge to the LDW. from the Marina. The southernmost of the Ttwo of the Marina outfalls areis owned by the Marina and discharge stormwater from the Marina property.; Tthe ownership of the northernmost Marina outfall is uncertain; howeverowned by the County and, the outfall drains the South Park Bridge (Windward 2009). Two storm drain outfalls to the south of T-117 are located on the Boeing South Park property and are owned by Boeing.; the northernmost of these two outfalls is in the vicinity of T-117). Stormwater in the Adjacent Streets and Residential Yards Study Area discharges to the City's CSS as described below. No combined sewer overflow (CSO) outfalls are located in the vicinity of the T-117 EAA ( Map 2-2); the nearest CSO (operated by King the County) is located at 8th Avenue S. King County records show that this CSO has not overflowed in the past 10 years (Huber 2009). Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 16 T-117 Upland Study Area The two storm drain outfalls along the shoreline of the T-117 EAA drain catch basins are located on the T-117 Upland Study Area and were field verified by the Port in 2006 (Phoinix 2007). Stormwater discharging through these outfalls primarily originates from the asphalt-paved T-117 Upland Study Area and is collected in the T-117 catch basins before discharge to the LDW. Stormwater runoff from the northern part of T- 117 Upland Study Area flows to a catch basin (CB-1) that discharges to the LDW through a 6 in diameter outfall located within the shoreline riprap. Runoff from the central and southern portions of the Upland Study Area drain to several catch basins (CB-2, CB-3, and CB-4) that eventually lead to a catch basin located to the northeast of the south building (CB-5) that discharges to the LDW. Roof drainage from the warehouse building on the south end of the T-117 Upland Study Area is conveyed from the gutters to the south side of the building and eventually discharges to the drainage ditch/swale located along the southern property boundary. Since completion of the 2006 TCRA, all of the catch basins on T-117 have been surrounded by hay bales and equipped with a filter sock. The catch basins include sumps for retaining settled solids and are equipped with inverted outlets to retain floating oil. These catch basins are inspected regularly as part of the 2006 TCRA inspection and maintenance program. In early September 2009, sediments that had accumulated inside and outside of catch basins on the T-117 Upland Study Area (CB-3 and CB-5) were sampled for dioxins and furans, arsenic, copper, silver, total petroleum hydrocarbons (TPH) in the diesel and gasoline ranges, PCBs, and polycyclic aromatic hydrocarbons (PAHs). In September 2009, all catch basins on the T-117 Upland Study Area were inspected and attempts were made to sample solids that had accumulated on both the outside (i.e., retained outside the catch basin by hay bales) and inside of the catch basins. Only CB-3 had accumulated sufficient solids both on the inside and outside for sampling; CB-5 had accumulated sufficient solids only on the outside. These samples were analyzed for dioxins and furans, arsenic, copper, silver, total petroleum hydrocarbons (TPH), PCBs, and polycyclic aromatic hydrocarbons (PAHs); and the results are presented on Table 2-1. Table 2-1. Summary of 2009 T-117 Upland Study Area catch basin sampling results Concentration CB-3 CB-5 ChemicalContaminant Ooutside Iinside Ooutside Metals (mg/kg) Arsenic 7 10.0 U 10.0 U Copper 121 146 131 Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 17 Concentration CB-3 CB-5 ChemicalContaminant Ooutside Iinside Ooutside Silver 5.2 4.2 2 Dioxin and Furans (ng/kg) Dioxin/furan TEQ 49.11 na 152.9 TPH (mg/kg) TPH diesel range 3,050 2,900 1,830 TPH gasoline range 14 na 5.6 PAH (mg/kg) cPAH TEQ 0.49 0.24 0.24 PCBs (mg/kg) Total PCBs 1.6 16 1.1 cPAH carcinogenic polycyclic aromatic hydrocarbon na not analyzed (insufficient sample volume) PAH polycyclic aromatic hydrocarbon PCB polychlorinated biphenyl TEQ toxic equivalent TPH total petroleum hydrocarbons U not detected at given concentration Based on the higher- than- expected concentrations of PCBs and dioxins and furans detected during Based on the September 2009 catch basin sampling event,results, site inspections were conducted in early November 2009 in order to better document the site stormwater drainage and potential sediment contaminant sources. Based on these inspections, Aa stormwater solids control plan (Chen and Hainsworth 2009) was developed as a result of these in inspections. The plan included and recommendationsed that site maintenance activities be performed to reduce potential sources of contaminants to stormwater and to reduce and /control the runoff of stormwater solids. Site maintenance was conducted in late December 2009 and included the following: Cracks in the asphalt cap throughout the site were sealed with asphalt sealer. Gaps above and below the ecology block retaining wall were sealed. Site vegetation was cut back. The asphalt surrounding all catch basins was washed down. The interiors of all catch basins were cleaned out. New hay bales and sediment filter socks were installed at all catch basins. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 18 The site maintenance activities were documented in the sixth semi-annual TCRA O&M report (AECOM 2009d), which was submitted to EPA on December 28, 2009, along with a catch basin sampling memorandum that described the September catch basin sampling events (Huntington and Hainsworth 2009). A vegetated drainage ditch/swale on the southern boundary between Boeing South Park and T-117 Upland Study Area also collects roof drainage from the warehousea building on the south end of the T-117 Upland Study Area. This ditch discharges to the shoreline mudflat area in the LDW. The runoff from the hillside along the Boeing property appears to flow east along the toe of slope and then enter the trench drain on the westsouth side of the building that eventually drains to CB-5 (Map 2-2). Adjacent Streets and Residential Yards Study Area Stormwater runoff from the Adjacent Streets and Residential Yards Study Area is currently collected in two separate systems that can be roughly divided into areas west and east of 17th Avenue S (see Map 2-2). To the west, runoff is currently discharged to the CSS. As part of its independent cleanup action in the Adjacent Streets in 2004 (see Section 2.2.4), the City installed a temporary stormwater collection and treatment system to control runoff from the newly paved streets and associated 1.8-acre catchment area adjacent to the T-117 Upland Study Area. The triangle of roadway that includes 17th Avenue S, Dallas Avenue S, and S Donovan Street currently drains to this temporary system, which is used to collect and s, store stormwater.s Retained stormwater is periodically released in , and batch discharges stormwater to the CSS at S Donovan Street and 17th Avenue S (Map 2-2). Because the CSS is over capacity in this area, stormwater is only discharged to the CSS during periods of dry weather to prevent sewer backups. During construction of the 2004 independent cleanup actions, a temporary stormwater treatment system was also installed to treat runoff during construction. Discharges to the CSS were permitted under a discharge authorization with King County Industrial Waste. Five 18,000-gal. storage tanks were installed to hold water for testing and to regulate the rate of stormwater discharge to the CSS. The permit (No. 4072-04) list conditions for both active stages and the non-active stage. Active stages are periods when active remediation and construction are occurring, and the non-active stage is the period of operation between interim and final removal actions. In addition to general stormwater permit conditions, special conditions of the permit for the non-active stage include the following: Collected stormwater must be pumped to appropriately sized settling tanks. Discharge must be monitored as follows: PCBs - monthly Discharge rate daily Discharge rate daily maximum monthly Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 19 Maximum discharge is 100,000 gallons per day The PCB discharge limit per Aroclor is 0.513 g/L (parts per billion). SPU must contact King the County at least 15 days before the NTCRA (removal action) project begins. Initial testing of stormwater solids in 2004 and 2005 resulted in occasional detections of PCBs up to 2.3 g/L. The treatment system was removed in April 2005 because the testing that has been conducted since January 2005 showed that PCBs were no longer detected (at a DL of 0.1 g/L) in stormwater runoff from streets adjacent to T-117. Stormwater continues to be discharged to the CSS via this system during dry conditions through a discharge authorization with the County. The County requires the stormwater to be tested each month when discharges occur. There has been one detection (0.12 mg/kg in January 2008) since treatment was discontinued (Appendix C). Under an arrangement with the Port, the City has a provision to discharge water from this system to the southern drainage system on the T-117 Upland Study Area as an emergency overflow during the rainy season (due to the over capacity condition of the CSS described above). Discharges to the Port system generally occur under the following conditions: Very Iintense storm events that exceed the capacity of the storage tanks Periods of prolonged rainfall, which cause the tanks to fill up when stormwater cannot be discharged to the CSS Cold weather conditions when the storage tanks and associated piping must be drained to prevent the pipes from freezing and breaking. When cold weather is predicted, the valves to both the CSS and the Port drainage system are fully opened to rapidly drain the system Since 2005, 11 emergency discharge events have occurred.2 Given the infrequent nature of the overflows to the LDW, SPU has not tried to develop direct correlations between rainfall events and overflows from the tanks. The tanks hold about 90,000 ft3 of runoff. The tanks fill up after approximately 2.25 to -2.5 in. of rain accumulates, either in a single event or multiple back- to- back storms. During the emergency discharges, runoff from the temporary system is discharged to a catch basin located at the northwest corner of the south building on the T-117 Upland Study Area. Runoff is conveyed in a pipe that runs along the north side of the building and discharges to the pavement at the northeast corner of the building. From there, runoff sheet flows approximately 60 ft across the pavement to CB-5 on the T-117 Upland Study Area. 2 The 11 discharges occurred on December 24 through- 27, 2005; January 1 through - 3, 2006;, January 6 through - 16, 2006; January 29 through -February 1, 2006; November 6 through - 30, 2006; December 12, 2006 - through January 5, 2007; January 7, 2007; December 3 through - 7, 2007; December 20, 20/07 through - January 2, 2008; January 15 through - 17, 2008; October 17 through - 19, 2009. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 20 The City intends to replace the temporary stormwater system with a permanent stormwater collection and treatment system in accordance with Seattle Municipal Code (SMC) 22.800 and Directors' Rule 2009-005 (SPU), 17-2009 (Department of Planning and Development [DPD]) (City of Seattle 2009b) as part of the removal action in the Adjacent Streets. Options for Aa new, permanent collection and treatment system to be installed in the Adjacent Streets following the removal action is included in the removal action alternatives describedare identified in Section 7. South Park Marina Properties Stormwater runoff from the south and east end of the Marina discharges directly to the LDW via a private drainage system (SAIC 2007b). The Marina operates a closedloop boat pressure wash system in the southeast portion of the property near the T-117 Upland Study Area. The wash system is located in the vicinity of the southern-most catch basin on the Marina property that discharges through a general stormwater National Pollutant Discharge Elimination System (NPDES)-permitted shoreline outfall fitted with an oil/water separator and a sand filter (StormwateRx) treatment system. The Marina has been sampling and analyzing the discharge from this outfall for oil and grease, total recoverable copper, and total suspended solids as required under its NPDES permit. Stormwater from the north end of the Marina property is believed to discharges directly to the LDW (Crow 2010). , although the private drainage system on the property has not been fully mapped (SAIC 2007b). The Marina's storm drain system is shown on Map 2-2.Because the onsite catch basins are near the LDW (as shown on Map 2-2) and downgradient from the CSS on Dallas Avenue S, stormwater from these catch basins is likely discharging to the LDW rather than being pumped to the CSS. However, further site investigation (e.g., dye testing) would be needed to confirm whether these onsite catch basins discharge to the LDW. Stormwater runoff from the Marina property located at the southeast corner of 16th Avenue S and Dallas Avenue S, which is used for additional dry boat storage, most likely enters the City catch basins located on 16th Avenue S, which convey stormwater to the City's CSS. Some drainage from this location may also flow onto Dallas Avenue S and into the LDW via the T-117 Upland Study Area catch basins. Boeing South Park To the south of the T-117 EAA at Boeing South Park, two privately owned outfalls discharge to the LDW. The northernmost outfall used to discharge non-contact cooling water from Boeing South Park under an NPDES permit. This practice was discontinued in 1993, and the cooling water was re-routed to the sanitary system (Ecology 1993b). Currently, both outfalls appear to discharge only stormwater; however, stormwater drainage patterns associated with Boeing South Park have not been identified. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 21 2.1.4 Current land use, zoning, ownership, and activities This section describes the current land use, zoning, ownership, and activities for the T-117 EAA. 2.1.4.1 Land-use, zoning, and ownership The T-117 EAA and vicinity are zoned3 as mixed-use for residential, commercial, and industrial activities (City of Seattle 2007a), as shown on Map 2-3. Current land use in the area is primarily manufacturing, commercial, and residential. Properties located on the east side of Dallas Avenue S in unincorporated King County include: The Marina, which is primarily used for boat storage and maintenance, as well as the moorage of live-aboard and recreational vessels. The upland portion of the Marina is currently owned and operated by South Park Marina Ltd. Partners. The eastwest portion of the Marina lies within the Duwamish Commercial Waterway District boundary. The former asphalt plant parcel, which is currently owned by the Port and was formerly used for manufacturing and industrial activities, including asphalt materials manufacturing. The site has been vacant since 2007. A portion of the Boeing South Park facility, which is currently owned by The Boeing Company and is primarily used as a training center. Properties to the west of Dallas Avenue S, include: The former Basin Oil plant (a used oil and antifreeze processing facility that ceased operations in 2004) at 8661 Dallas Avenue S, which is currently owned by Basin Oil Company. This property was residential prior to being used for industrial purposes. A property at 8617 17th Avenue S formerly used by Basin Oil for excess drum storage until this parcel was purchased by the Marina for boat storage in August 2007. This property was residential until November 1998 when it was sold to Basin Oil and was subsequently used for industrial purposes. The former residential parcel located at 8603 Dallas Avenue S used by the Marina for boat storage. Commercial and residential parcels bounded by Dallas Avenue S, 16th Avenue S, and S Donovan Street, including three commercial parcels (and a boat storage area), two residential parcels, and one apartment complex. West of 16th, there are 22 residential and six commercial parcels on the east side of 14th Avenue S. A commercial/warehouse facility at 8620 16th Avenue S. The property has been occupied by Caff Umbria Inc. (a wholesale coffee roaster) since 2008. Former occupants were the Seattle Chocolate Company (a chocolate confectionery 3 Zoning designation based on a 2002 City of Seattle GIS layer, as shown on Map 2-2. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 22 company that ceased operations in 2007), Allied Bolt Company (metal fabrication), and Fasteners, Inc. (metal fabrication). The Basin Oil parcels and the Boeing South Park parcels within the City limits are zoned as manufacturing/industrial; the parcels between 16th Avenue S and 17th Avenue S are zoned as industrial buffer. Parcels west of 16th Avenue S and north of S Donovan Street are zoned as residential/commercial and include approximately 20 houses and one 12-unit apartment complex (Map 2-3). 2.1.4.2 Commercial and residential activities As previously described, there are several residences as well as various commercial and manufacturing facilities within the vicinity of T-117 EAA. Because the T-117 Upland Study Area and T-117 Sediment Study Area have restricted access, public activities within these areas are limited. Access to the Sediment Study Area is restricted by a secure fence surrounding the T-117 Upland Study Area, but is accessible from the LDW by boat and kayak. The Muckleshoot Tribe has a commercial salmon fishery in the LDW, uses portions of the T-117 Sediment Study Area for tribal fishing, and thus may come in contact with the sediment. Within the Adjacent Streets and Residential Yards Study Area, residential activities could include, but are not limited to, recreation activities such as jogging or biking, or typical residential activities such as walking, yard work, or driving. Workers may also access the T-117 EAA to service utilities, which may require digging in the Adjacent Streets as well as on the T-117 Upland Study Area. Exposure scenarios associated with these site uses are evaluated in Section 3.2. 2.1.4.3 Recreational activities The LDW is not a major recreational resource compared to other water bodies in and around the City (King County 1999b). The Duwamish River Cleanup Coalition, a consortium of environmental and citizen groups that participate in cleanup efforts, has coordinated activities to improve habitat and recreational activities. The group has been conducting kayak tours on the LDW and asserts, but anecdotal evidence from community members suggests that recreational use of the LDW has been increasing, including guided kayak tours of the LDW and shoreline access at new parks and restoration sites (EPA 2010). Few data that quantify the frequency with which people use the river for recreational purposes have been identified. The County's human health risk assessment (HHRA) (King County 1999b) discussed the human use of both the LDW and Elliott Bay, but presented quantitative data only for fishing. The County study assumed that few, if any, people engage in activities such as swimming, scuba diving, and windsurfing within the LDW. There are several public access points along the LDW and recreational boating and kayaking in the LDW have been observed as part of a survey for the LDW RI (Windward 2005b). The Marina and a public boat launch north of the Marina are the closest recreational boating access points to the T-117 EAA. There is no known use of T-117 as a boat put-in or haul-out location. Such Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 23 use is unlikely because the T-117 shoreline is steep and overgrown and the T-117 Upland Study Area is secured by a fence. However, the T-117 shoreline and intertidal mudflat is accessible from the LDW by boat. In the County survey of fishing and seafood consumption practices (King County 1999b), none of the LDW sites identified as locations where recreational fishing occurred were near the T-117 EAA. However, recreational fishing may occur from the Marina or from boats in the vicinity of the T-117 EAA. There are no recent data on seafood consumption rates specific to the LDW, but current consumption rates may be suppressed. There are several possible explanations for such suppression, including the current advisory against the consumption of resident fish and shellfish, media coverage of the published risks from the consumption of LDW seafood, and the close proximity of more desirable fishing locations outside the LDW. The T-117 EAA is within tribal Usual and Accustomed fishing areas, and the tribes desire the restoration of shellfish and fisheries resources. 2.1.5 Physical environment This section describes the physical features associated with both the aquatic and upland portions of the T-117 EAA. Sections 2.1.5.1 and 2.1.5.2 discuss the aquatic portion of the site; Section 2.1.5.3 focuses on the upland environment. 2.1.5.1 Currents, circulation, and estuarine features River currents in the Sediment Study Area have not been specifically measured. However, the results of a site-wide hydrodynamic model developed as part of the LDW RI (Windward 2007c) can be generally applied to T-117 insofar as the model provides information regarding the currents of the LDW as a whole. The model may be less useful for capturing hydrodynamics in near-shore and shallow areas within the T-117 Sediment Study Area. Water currents within the LDW are driven by tidal actions and river flow; the relative influence of each is highly dependent on seasonal river discharge volumes. Fresh water flowing downstream overlies the tidally influenced salt water that enters the system. The LDW is tidally influenced to the head of the estuary at RM 12.0 (Kerwin and Nelson 2000), with the degree of tidal influence varying depending on stream flow and tidal stage. Tidal action significantly influences currents and water elevation in the LDW. The average tidal range is -0.91 to 12.81 ft MLLW.4 Typical of tidally influenced estuaries, the LDW has a relatively sharp interface, or wedge, between the freshwater outflow at the surface and saltwater inflow at depth. Tidal effects and the volume of river flow also control the movement of the saltwater wedge. The toe of the saltwater wedge is 4 Information based on National Oceanic and Atmospheric Administration (NOAA) Center for Operational Oceanographic Products and Services National Tidal Datum from 1993 to 2003. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 24 generally located between Slip 4 (approximately 0.8 RM north of T-117) and Turning Basin 3 (approximately 1 RM south of T-117) (Santos and Stoner 1972). Salinity measurements by Santos and Stoner (1972) at RM 3.2, just downstream from T-117, indicated that at this location, the estuary had freshwater at all points in the vertical profile only when there was a combination of very low tide and high rates of river flow. Dye studies indicated that downward vertical mixing over the length of the saltwater wedge was almost nonexistent (Schock et al. 1998). The Green River is the main source of water for the LDW. Average downstream flow for the Duwamish River measured at the Tukwila gauging station was 1,533 cubic feet per second (cfs) during 2003-2004, ranging from 327 cfs in August to 3,290 cfs in June (Clemens 2007). Flow at the Auburn gauging station ranged from 152 to 11,600 cfs (the record high) between 1962 and 2004 (Clemens 2007). Between 2000 and 2006, the annual average flow rate measured at the Auburn gauging station was 1,190 cfs, ranging between 850.6 cfs and 1,413 cfs (USGS 2007). Flow rates are greatest in the winter because of seasonal precipitation and lowest throughout the late summer dry season. Stream flow to the LDW is also influenced by water diversions, particularly by the City of Tacoma's Headworks Dam, located on the Green River, which diverts at least 113 cfs daily for municipal use. The Howard Hanson Dam (located upstream of the City of Tacoma's Headworks Dam) also influences flows in the river. Information on the estimated influence of the Howard Hanson Dam on flow rates (Kerwin and Nelson 2000) indicates flow rates in the Duwamish River have been reduced by 33 to 60%, depending on the season. The historical diversion of the White, Black, and Cedar Rivers from the Green/Duwamish River system resulted in a reduction of contributing flow by approximately 70% to the system, and an a accompanying reduction in total discharge for the Duwamish River. LDW Stream flow is also influenced by inflows from surface water sources such as storm drains, CSOs, tributary creeks, and nonpoint inputs, although these sources are expected to be less than 1% of the total discharge, even during peak flow events (Windward 2007c). Two main tributary creeks drain into the LDW: Puget Creek at approximately RM 0.7 (downstream of the T-117 EAA) and Hamm Creek at approximately RM 4.2 (upstream of the T-117 EAA). 2.1.5.2 Sediment transport LDW-wide investigations have been conducted that provide some insight into hydrodynamic and sediment transport conditions at T-117 within the river. Sediment transport within the LDW, including the T-117 EAA, is influenced by many variables, including hydrodynamic forces attributable to currents and circulation driven by tidal actions and river flow, the saltwater wedge, sediment loading from upstream and upland sources, channel morphology, and resuspension processes (i.e., propeller scour, bioturbation, bed shear stress, and dredging). As part of the LDW RI, sediment transport data were collected throughout the LDW (Windward and QEA 2005) to Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 25 enable a better understanding of the LDW sediment transport process and the development of a LDW-wide sediment transport model (STM) (QEA 2008). The results of these investigations and analyses can also be used to evaluate sediment transport conditions in specific areas of the LDW, such as the T-117 EAA, but the accuracy of the model at such small scales is highly uncertain. Consequently, predictions from the STM for the T-117 Sediment Study Area did not influence the development of removal action alternatives. The LDW-wide STM indicated that the T-117 Sediment Study Area was net depositional over annual time scales. Along most of the T-117 Sediment Study Area, the predicted net sedimentation rate for a 30-yr period ranged from 0 to 0.5 cm/yr, except along the northern portion of the T-117 EAA at the Marina interface, where the net sedimentation rate was estimated to be > 3 cm/yr. The LDW-wide STM included simulations of high-flow events (i.e., events with return periods of 2, 10, and 100 years) that occur over time scales of several days and simulations that focused on sediment deposition patterns over longer time scales (i.e., 30 years). A separate model was used to evaluate ship-induced mixing of surface sediment (QEA 2008). The simulation of high-flow events indicated that in the southern and central portion of the Sediment Study Area, no more than 2 cm of net erosion is estimated to occur during the 2- and 10-yr high flow events (Map 2-4), while up to 6 cm of net erosion is estimated to occur during the 100-yr event (Map 2-4). In contrast, no net erosion is predicted for the northern portion of the site, even during the 100-yr high-flow event (Map 2-4). The LDW-wide STM evaluated deposition patterns over a 30-yr time scale. Although short-term events such as those described above may cause periodic erosion, results of the longer-term analysis indicated that the T-117 EAA Sediment Study Area was net depositional over annual time scales. Along most of the T-117 EAA, the predicted net sedimentation rate for a 30-yr period ranged from 0 to 0.5 cm/yr, except along the northern portion of the EAA at the Marina interface, where the net sedimentation rate was estimated at > 3 cm/yr (Map 2-5). Although the results from this LDW-wide modeling effort provide insight into broader trends in the vicinity of the T-117 EAA, the spatial heterogeneity of the model predictions within and adjacent to the T-117 EAA suggests that the area is in a transitional location with regard to both erosion and sedimentation rates. The modeling results also indicate that some net erosion, on the order of 0 to 6 cm, may occur along most of the T-117 EAA shoreline during high-flow events, but net deposition may occur in the vicinity of the Marina. The investigations of ship traffic presented in the STM report indicated that ship activity is not a major cause of sediment transport in the LDW (except in ship berthing areas) or in the T-117 EAA (QEA 2008). Several organizations have measured current velocities within the LDW as part of environmental investigations. The most extensive measurements within the LDW have been conducted by the County. Current velocity meters were placed at two Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 26 locations in the LDW (RM 1.1 and RM 3.5) for a 3-month period and recorded currents at 15-minute intervals along a vertical profile (King County 1999a). During this study, measured current velocities within the LDW rarely exceeded 40 cm/s (1.3 ft/s). Another study of current velocities involved the deployment of two current velocity meters for two 4-week periods at RM 1.1, which is a straight portion of the LDW located just south of Kellogg Island (King County 2005). One meter was placed near the center of the navigation channel; the other was placed on a shallower channel side slope. Reported mean net current speeds for meters placed in the center of the channel ranged from 2.5 cm/s (0.082 ft/s) (at 25% channel depth) to 18 cm/s (0.59 ft/s) (at 10% channel depth). Mean net current speeds for meters placed at the channel side slope locations ranged from 1.3 cm/s (0.043 ft/s) (at 25% depth) to 8.9 cm/s (0.29 ft/s) (at 10% depth). Currents were predominately oriented along the channel, and velocities were generally slower along the side slopes. 2.1.5.3 Geology Geology of the Duwamish Basin The Greater Duwamish Valley was formed by the carving action of glaciers that last advanced into this area from British Columbia approximately 15,000 years ago. When the ice sheets began to retreat approximately 5,700 years ago, the waters of Puget Sound extended up the Duwamish Valley as far south as Auburn, about 32 km (19 mi) upstream of the present mouth of the LDW at Elliott Bay. Around that same time, the Osceola Mudflow descended from Mount Rainier, depositing a massive layer of sediment into the then marine waters near present-day Auburn and Kent. The mudflow diverted the historical course of the White River, at that time a tributary of the Puyallup River, to the Green River (Booth and Herman 1998). The alluvial fill within the Duwamish Valley deepened over time from the deposition of upstream fluvial sediments of the White, Green, and Black Rivers, advancing the mouth of the Duwamish River farther to the north. The fill included beds of fine silts and sands deposited as riverine and floodplain deposits, with coarser sands and gravels deposited near the water's edge. These sediments eventually buried the post-glacial form of the valley so that only a few outcroppings of bedrock remain exposed at the ground surface. As the river flooded and migrated back and forth across the floodplain, these sediments were re-deposited by the river and continually intermixed with additional riverine and floodplain deposits (Booth and Herman 1998). In the late 1800s and early 1900s, extensive modifications were made to the river, including the filling of tide flats and floodplains to straighten the river channel, resulting in the abandonment of almost 6 km (3.7 mi) of the original meandering river bed (Map 2-64). Several current side slips in the LDW are remnants of these old river meanders. The channel was dredged for navigational purposes, and the excavated material was frequently used to fill the old channel areas and the lowlands to bring them above flood levels. The portion of the LDW at the T-117 EAA was a new Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 27 alignment, dredged and excavated as part of the "straightening" of the river. A former filled meander (oxbow) intercepts the shoreline in the vicinity of the north portion of T-117. Because the dredge fill materials were similar to the native deposits, they are difficult to distinguish from the native silts and sands. Subsequent filling of the lowlands for continued development resulted in a surficial layer of fill over most of the lower Duwamish Valley. Although the sediment types encountered in the LDW are variable (either from changing regional or local hydrodynamics or anthropogenic disturbances), basic sedimentary patterns of interbedded silts and sands are present in the LDW (Booth and Herman 1998). The three principal geologic assemblages within the Greater Duwamish Valley that establish the regional hydrogeologic system, from oldest to youngest, are: Bedrock Glacial and non-glacial sedimentary units (glacially overridden and dense units that make up the plateaus to the east and west of the Duwamish Valley) Undifferentiated quaternary alluvial deposits (principal aquifer and groundwater pathway for the Duwamish basin) Bedrock Bedrock in the Greater Duwamish Valley provides the lower boundary of the aquifer system and limits groundwater flow in the basin. At the north end of the Duwamish Valley, the elevation of the bedrock unit ranges from roughly 60 m (200 ft) to over 500 m (1,640 ft) below ground surface (bgs). Exposed bedrock in the eastern and southern areas of the Duwamish Valley is predominantly marine and continental sedimentary rocks intermixed with isolated areas of igneous rock deposited during the Tertiary period. Sedimentary rock units within the Greater Duwamish Valley are not an important source of groundwater because the predominantly cemented, fine-grained nature of the material precludes rapid groundwater movement. However, igneous rock layers are extensive in the area and can store and move water much more readily (Booth and Herman 1998). Glacial and Non-Glacial Sedimentary Deposits The glacial and non-glacial sedimentary units within the Duwamish basin are complex sequences of interbedded and unconsolidated deposits. In areas where bedrock occurs at significant depth below the river valley, these glacial sedimentary deposits serve as the lower boundary of the alluvial deposits in the Greater Duwamish Valley. The upland plateau areas to the east and west of the valley are formed predominantly of these glacially deposited sedimentary units (Booth and Herman 1998). Little information on the glacially overridden sedimentary units within the LDW study area is available. These overridden deposits are mainly fine-grained materials; their maximum depth is unknown (Booth and Herman 1998). Although these deposits provide a geologic boundary to the overlying alluvial deposits, they also provide a Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 28 potential hydraulic pathway for the flow of upland groundwater to the Duwamish Valley alluvial sediments. Thick sequences or silt beds (transitional beds) could potentially limit the upland inflow of groundwater where these deposits occur. The presence of saline water in the deeper alluvial sediments outside of current tidal influence areas suggests that there is little influx of fresh water into the original marine delta deposits. The lack of fresh groundwater in these deep alluvial sediments may indicate that the inflow of upland groundwater in this layer is limited (Booth and Herman 1998). Duwamish Valley Alluvial Deposits The near-surface alluvial deposits in the Duwamish River valley extend to a depth of roughly 60 m (200 ft) bgs within a trough bounded between the bedrock unit and the very dense upland glacial and non-glacial sedimentary deposits. The geologic history of this valley suggests that the alluvial deposit sequences include estuarine deposits, typically fine sands and silts (often including shell fragments), which progress upward into more complex, interbedded river-dominated sequences of sand, silt, and gravel. These layers of alluvial deposits delineated the areas of advancing river delta sedimentation that increase in thickness from south to north (Booth and Herman 1998). Geology of the T-117 EAA and Vicinity A summary of geotechnical information for the west shore of the LDW indicates that upland portions of the T-117 EAA consist of shallow fill. The alluvium underlying the fill extends to a depth of approximately 95 ft (29 m) bgs and consists of discontinuous silt units with interbedded sands, silty sands, and some gravel. Thin peat deposits have also been encountered. A fine-grained lower unit that contains shell fragments has been observed in borings beneath the lower silt, and dense sand and gravel were reportedly observed at depths below 95 ft (29 m) bgs (Wilbur Consulting 2003). A Geologic cross sections of the T-11 EAA areis provided as Figures 2-1 through 2-5. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 29 Slipsheets (11 x 17) Figure 2-1. Geologic cross section of the T 117 EAA Figure 2-1. Cross section locations Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 31 Slipsheet (11 x 17) Figure 2-2. Geologic cross section A-A of the T-117 EAA Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 33 Slipsheet (11 x 17) Figure 2-3. Geologic cross section B-B of the T-117 EAA Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 35 Slipsheet (11 x 17) Figure 2-4. Geologic cross section C-C of the T-117 EAA Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 37 Slipsheet (11 x 17) Figure 2-5. Geologic cross section D-D of the T-117 EAA Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 39 Geology of the T-117 Upland Study Area and Adjacent Streets According to the results of previous site characterization activities at the T-117 Upland Study Area (Parametrix 1991; RETEC 2007b; SECOR 1997; Windward and DOF 2006), subsurface soil at the T-117 EAA consists of fine to medium sand, sand/silt mixtures, and silt. Shallow soils typically consist of fill material that ranges from 3 to 10 ft in thickness, with the fill thickness increasing toward the LDW. This fill consists of sand with varying amounts of silt mixed with anthropogenic materials (e.g., bricks, rubble, and wood). Shallow boreholes typically terminate in a silt unit present beneath the fill. All stratigraphic information from below the fill/silt contact has been provided by a geotechnical borehole advanced along the west bank of the LDW (Hart Crowser, 2003). This borehole indicated that the silt unit is 10 ft thick and is underlain by a sand unit that is about 20 ft thick. Silt and sand interbeds are present beneath the sand unit. A bedrock outcropping, which is unique within the Duwamish valley, is present immediately south of the T-117 EAA (Booth and Herman, 1998). This bedrock was has been encountered during geotechnical explorations on the Boeing South Park property at elevations above 40 ft MLLW ( Dames and Moore, 1980a and b), which is above the ground surface elevation of the T-117 Upland Studay Area the installation of MW-13 by Ecology. The influence of this formation can be seen in the upper elevation of the till in the geologic cross sections (Figures 2-1 through 2-5). This formation may also influence local hydrogeology. T-117 Upland Study Area soil has been modified by the 1999 and 2006 TCRAs. The removal area that was excavated for the 1999 TCRA (Onsite 2000a) was backfilled with fill and quarry spalls (i.e., large angular rocks) to depths ranging from approximately 2 to 6 ft. This backfill was overlain with an asphalt pavement system (i.e., gravel subgrade and bituminous pavement) that was approximately 1 ft thick. The removal area that was excavated for the 2006 TCRA (RETEC 2007b) was backfilled with crushed rock to depths ranging from approximately 2 to 7 ft and covered with asphalt pavement. Site characterization work conducted by the City in the Adjacent Streets determined that the soil gradation is generally fill material (asphalt and gravel with fines) in the top 1 to 2 ft underlain by silts, sandy silts, and a characteristic native sand deposit observed throughout most of the site (Integral 2006b). The depth to the native sand unit varied approximately as follows: 4 to 6 ft at Dallas Avenue S, between 14th Avenue S and 17th Avenue S 2 to 5 ft at Dallas Avenue S, between 17th Avenue S and S Donovan Street 9 to 10 ft at S Donovan Street, between 17th Avenue S and Dallas Avenue S Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 41 2.1.5.4 Hydrogeology The shallow unconfined aquifer in the Duwamish River valley is generally located within the native alluvium unit. At T-117, shallow groundwater extends upward into the overlying sand and silt fill, and water table fluctuations are influenced by river level fluctuations in the LDW. Groundwater is recharged from the upland areas to the west (Wilbur Consulting 2003), and net groundwater flow is toward the LDW as shown on Map 2-75. Recent groundwater level data collected in 2008 and 2009 (ENSR|AECOM 2008; AECOM 2009a) indicate that the groundwater table within the T-117 EAA occurs between approximately 7.4 and 13.0 ft MLLW (Map 2-75). Tidal influence has been observed in all monitoring wells on the T-117 Upland Study Area (MW-2 through MW-8) and was confirmed by tidal study piezometric measurements made in 1998, 2003, 2006, and 2008 (SECOR 1998; Windward et al. 2005b; Windward unpublished; ENSR|AECOM 2008). During these tidal studies, the water levels in the LDW varied by up to 13 ft, from extreme high to extreme low tide, and water levels in the T-117 shoreline wells typically varied by 3.2 to 8 ft. The magnitude of the water level variation decreased inland with no tidal influence observed in the wells located on Dallas Avenue S (MW-01, MW-09, and MW-10) (ENSR|AECOM 2008). Based on this information, tidal influence becomes negligible somewhere between about 80 ft (MW- 03) and 230 ft (Dallas Avenue S) from shore. An earlier investigator reported that the tidally influenced area adjacent to the waterway is generally within 300 to 500 ft of the shoreline (Booth and Herman 1998). At T-117, the groundwater gradient reverses during high tide, causing water from the LDW to flow into the aquifer and mix with groundwater. Once the tide has ebbed, groundwater flowing from the aquifer into the LDW is a mixture of groundwater and surface water from the LDW. The degree to which surface water enters and exits the aquifer during the tidal cycle has ramifications for groundwater characterization. Tidal influence was measured in all shoreline wells and in well MW-03, which is located approximately 100 ft from the LDW (Map 2-75). In addition, the use of a pumping well at this location could create a drawdown at significant distance, though much less than the 1,000 ft noted by Herman and Wineman (1997). Under these conditions, the infiltration of surface water from the adjacent LDW would occur across the entire vicinity of the T-117 Upland Study Area. Appendix B discusses this issue in more detail and provides an estimate of tidal mixing based on empirical data and modeling studies. Groundwater and surface water interactions also affect the salinity of the groundwater at the T-117 EAA. Specific conductance, a proxy for salinity, is elevated in shoreline wells. This is likely due to the infiltration of brackish surface water from the LDW. Specific conductance is also elevated in several other wells that are not adjacent to the LDW. The highest specific conductance measurements were taken at MW-13, which is located near a bedrock outcropping at the Boeing property to the south. It is likely that Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 42 the elevated specific conductance is due to upwelling of more saline groundwater from the lower aquifer along preferential flow paths adjacent to the bedrock in the vicinity of MW-13 (Booth and Herman 1998). The lower aquifer in this area is more saline because of historical interactions with Puget Sound (Herman and Wineman 1997) (see Appendix B for a full discussion of specific conductance in groundwater at the T-117 EAA). Horizontal groundwater gradients were determined based on the net groundwater flow (Map 2-5). Two horizontal gradients were determined for the site, one between MW-10 and MW-12 and a second between MW-03 and the shoreline well MW-05R. The horizontal gradient in the vicinity of MW-10 and MW-12 is 0.076 ft/ft, and the horizontal gradient in the vicinity of MW-03 and MW-05R is 0.009 ft/ft. Hydraulic conductivities for typical silty sand units, such as the T-117 EAA fill soil, range from 10-1 to 10-5 cm/s. Site- specific data for groundwater in the upper portion of the native alluvium was used to estimate Silt units, such as the upper portion of the native alluvium that is immediately below the fill unit, typically have hydraulic conductivities ranging from 10-3-1 to 10-7-3 cm/s (Freeze and Cherry 1979). Seeps have been observed at the base of the shoreline riprap (at the mudline) near the central portion of T-117 Sediment Study Area and south of the Marina boat ramp during low tides. Two seeps appear to be well established, as demonstrated by the channels that have been cut into the tide flats between the seep locations and the main river channel. Several minor seeps have also been observed along the T-117 EAA shoreline, but the flow is intermittent and not as pronounced. One of the well established groundwater seeps (Seep 2 (SW-2), shown on Map 2-1) appears to emerge adjacent to a wooden pile, which suggests that the pile may have intercepted a locally confined lower sand unit. The possible sources and control of these seeps will be addressed during the remedial design phase of the NTCRA. 2.1.6 Sensitive ecosystems and habitat Sensitive ecosystems and habitat in the T-117 EAA are limited to the aquatic sediment portion of the site. The upland portion of the EAA is developed and lacks sufficient substantial habitat to support wildlife, as described in a terrestrial ecological evaluation (TEE) conducted for the Adjacent Streets (Integral 2006b). Estuarine intertidal and near-shore subtidal ecosystems in the LDW provide important habitat for juvenile salmonid growth, physiological transition, and predator avoidance during their outmigration. The estuarine environment also provides refuge for various marine fish during larval stages and supports an array of preferred prey for all salmonid life stages. The intertidal zone in the LDW is located approximately between -4 ft and +13 ft MLLW, and the near-shore subtidal zone is just slightly deeper than the intertidal zone. Within the intertidal areas, mudflats serve many ecosystem functions, including providing food and habitat for benthic invertebrates, fish, shorebirds, and aquatic Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 43 mammals. A diverse assemblage of invertebrate species, including larvae, clams, worms, and crustaceans, can be found in these habitats, which typically consist of unconsolidated silts and clays and sand flats of unconsolidated sandy sediments (Simenstad et al. 1991). Mudflats containing gravel may support high densities of bivalve populations. The features of the T-117 EAA intertidal mudflat make the area suitable habitat for the organisms described above as well as provide potentially important habitat for organisms within the juvenile salmonid food web. The intertidal mudflat of the T-117 EAA extends approximately 15 to 65 ft (4.6 to 20 m) from the immediate shoreline, around +5 ft MLLW, to a depth of approximately -4 ft MLLW. The T-117 intertidal mudflat includes more than 43,000 ft2 (4,000 m2) of gently sloping, fine-grained sediment. An LDW clam survey (Windward 2004) conducted in 2003 identified harvestable clams within the T-117 intertidal area. 2.2 PREVIOUS REMOVAL ACTIONS This section provides an overview of historical removal action activities and environmental investigations pertinent to the T-117 EAA. Prior to the Port's acquisition of the asphalt plant T-117 Upland Study Area parcel in 20001999, the Malarkey asphalt plant was closed, and a number of storage tanks were removed or abandoned (i.e., closed in place) as required by EPA in a 1996 AOC for Removal Action at Malarkey (EPA 1996a). In 1996 and 1997, Malarkey performed tank and equipment decommissioning and decontamination and removed soil from ditch areas and the utility corridor (i.e., hot spot removals). Product also was also removed from a large-diameter well prior to Port ownership (SECOR 1998). All of the tanks were decommissioned and removed from the property prior to the Port's acquisition in 20001999. The three USTs, which contained diesel and waste oil, were filled with concrete slurry and closed in place; a partially buried railroad car, which was used to hold waste oil, was excavated and removed. Sixteen ASTs were also removed from the site. Soil samples were taken from the tanks and tested for TPH (Hart Crowser 1992). The former locations of these tanks are shown on Map 2-86. In 1999, immediately prior to the Port's acquisition of the site, a TCRA for upland soil was conducted within the T-117 Upland Study Area pursuant to an EPA AOC (No. 10-2000-0222) (EPA 2000) to remove PCB-contaminated soil from the former ponding area (see Section 2.2.1 for additional details). Since the 1999 TCRA and the Port's 2000 acquisition of the former asphalt plant, several actions that focus on the removal of asphalt plant residues and PCB-contaminated soil from within the T-117 Upland Study Area and Adjacent Streets have been performed by the Port. In 2003, several old drums and other large debris were removed from the offshore intertidal area. In 2004, a below-grade utility corridor was cleaned out. In 2006, under the terms of a separate ASAOC, the Port carried out an additional TCRA to remove additional Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 44 impacted soil with the highest concentrations of the newly discovered PCBs within the T-117 Upland Study Area. In 2004 and 2005, the City implemented a series of independent cleanup actions to address PCBs discovered in soil in the Adjacent Streets and Residential Yards and three neighboring residential properties near the T-117 EAA (City of Seattle 2005). The City removed soil that had PCB concentrations exceeding 1 mg/kg from the residential yards and unpaved street shoulders and placed a temporary asphalt cap over residual contamination within the street ROW areas. The action level of 1 mg/kg was based on the MTCA Method A CUL for PCBs. The current removal actionNTCRA boundary for the Adjacent Streets includes the areas whereaddresses remaining contamination may still be presentin this area. The above removal actions conducted in the T-117 EAA are described in greater detail in the following subsections. The locations of previous removal actions are shown on Map 2-86. Removal actions conducted in the T-117 EAA are also presented on the timeline (Figure 1-1). 2.2.1 1999 TCRAtime-critical removal action PCBs were initially detected in surface and subsurface soil in the upland shoreline parcel (former ponding area) during several investigations in the 1990s. A TCRA (Map 2-86) was conducted by the Port in 1999 (Onsite 2000a) to remove PCB contaminated soil from an area within the shoreline parcel that contained elevated concentrations of PCBs based on previous sampling efforts (SECOR 1998, 1997). The TCRA was performed in accordance with the EPA AOC (No. 10-2000-0222) (EPA 2000) and associated SOW. Tasks included: Mobilization and site preparation (including installation of drainage controls and the establishment of controlled work areas) Removal, storage, testing, and treatment of water from the ponding area prior to soil removal Containment, testing, and removal (for offsite treatment) of approximately 50,000 gal. of water during excavation Removal from the work area and disposal of several drums that contained asphalt Excavation and disposal of 2,061 tons of contaminated soil with PCB concentrations that ranged up to 500 mg/kg Removal of shallow (i.e., top 0.5 ft) soil from exposed areas around the former asphalt plant structures Backfilling Installation of an asphalt pavement cap Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 45 Improvement of storm drains (e.g., new catch basins in excavated area) Abandonment of the large-diameter industrial water supply well Replacement of three monitoring wells removed during the soil excavation All material removed from the property was disposed of at approved facilities. The project's target action level for PCBs in soil was 25 mg/kg, and remaining soil at the T-117 Upland Study Area was capped with asphalt pavement. The project's target action level was negotiated with EPA and was premised on the "spill cleanup policy" value (25 mg/kg) for soil in restricted-access sites set forth under the Toxic Substances Control Act (TSCA). However, concentrations of PCBs above the action level were left in removal grids A-1 and B-2 (Map 2-86) because of the potential undermining of old building foundations. A 375-gal. (1,420-L) non-leaking diesel tank was also discovered during the project and removed (Onsite 2000a). Two soil samples from the tank excavation had elevated concentrations of diesel-range TPH (TPH-D) (462 and 2,780 mg/kg). Other samples did not contain detectable concentrations of TPH. 2.2.2 2004 utility corridor cleanout The Port removed contaminated and structurally unsuitable fill materials, debris, and waste from approximately 150 ft of a 2-ft-wide, 2.5-ft-deep, below-grade utility corridor in the T-117 Upland Study Area (Map 2-6). This project was conducted independently by the Port, without oversight under either the MTCA or CERCLA. The work was conducted to prevent further settling of the pavement surface along the concrete-lined corridor and to stem extrusions of asphalt material that were caused by heavy vehicles (high surface loading) during warm weather and appeared at several locations along the alignment. Soft asphalt was observed extruding up through the pavement in the truck parking area and there was concern that this material could be tracked and spread by vehicles. This project was conducted independently by the Port without oversight under either the Model Toxics Control Act (MTCA) or CERCLA. The Port removed the residual asphalt, contaminated soil, debris, and abandoned asphalt plant-era pipes and backfilled the corridor with controlled density fill, without oversight under either the MTCA or CERCLA. The overlying surface was repaved with asphalt to restore the pavement surface. Soil removed from the south portion of the concrete-lined corridor was found to contain elevated concentrations of TPH-D and lube oil-range TPH (TPH-O), as well as large amounts of roofing asphalt. Concentrations of PCBs in excavated soil did not exceed 10 mg/kg, and the soil was not designated as a dangerous waste as a result of PAH or metals concentrations. Approximately 26 tons of TPH-contaminated soil were excavated and disposed of offsite at an approved landfill. Asphalt, pipe and metal debris, and oil were also removed (Windward and Onsite 2004). All material removed from the property was disposed of, treated, or recycled at approved facilities. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 46 2.2.3 2006 time-critical removal actionTCRA The Port conducted a second TCRA (Map 2-6) to remove hazardous substances from the T-117 Upland Study Area from September to November 2006. EPA determined that a TCRA was required because of the high concentrations of PCBs in soil on the T-- 117 Upland Study Area. The objectives of the TCRA were to prevent or reduce the potential for human exposure to contaminants and to prevent or reduce the potential for contaminants to migrate into the LDW. The TCRA was performed in accordance with the Superfund ASAOC (No. 10--2006-- 0072) SOW (EPA 2006b). The TCRA included the excavation of PCB-contaminated soil, offsite disposal of PCB-contaminated soil at approved landfills, offsite disposal of construction debris (e.g., asphalt), backfilling of excavations with clean soil, environmental controls, monitoring to ensure there were no releases of PCB-- contaminated soil to the adjacent neighborhood and to the LDW, and site restoration (e.g., new asphalt cap, street sweeping). TCRA activities were overseen by EPA and closely coordinated with EPA and the neighborhood, with regular meetings being held throughout the duration of the project. Three areas with elevated PCB concentrations (up to 9,200 mg/kg) were excavated: one area along the riverbank and two areas west of the riverbank (Map 2-6). Excavation along the riverbank consisted of the removal of the upper 2 ft of surficial soil, including the existing asphalt and pavement. Excavation depths in the remaining two areas varied from 2.5 to 7 ft bgs based on the depth needed to achieve the PCB removal action level of 25 mg/kg (RETEC 2007b). All material removed from the property was disposed of, treated, or recycled at approved facilities. The following quantities were removed: 3,030 tons of Toxic Substances Control Act (TSCA) soil (concentrations > 50 50 mg/kg total PCB) 78 tons of Resource Conservation and Recovery Act (RCRA) Subtitle D (concentrations < 50 mg/kg total PCB) soil 533 tons of RCRA Subtitle D asphalt and concrete debris 91,472 gal. of onsite runoff/decontamination water 2.7 tons of metal debris 1.2 tons of cleared and grubbed vegetative debris Clean backfill was placed in all of the excavation areas after the analytical results for each excavation area had been reviewed. A non-woven geotextile was installed on top of the excavation subgrade as an identifying marker layer. Asphalt pavement (i.e., a temporary cap) was installed after the backfill had been placed and compacted (RETEC 2007b). Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 47 In 2008, bank repair work was performed as part of maintenance activities associated with the TCRA. This work included stabilizing approximately 25 linear ft of the upper shoreline bank by reinforcing the area with a riprap revetment. In addition, to minimize erosion, clean gravel was removed from the top of the bank to reduce the load on adjacent areas of the bank. The localized bank failure was first noted during a scheduled maintenance visit on March 7, 2008. A temporary repair of the bank was implemented on March 13, 2008, which included covering the eroded area with plastic and securing the plastic with sandbags. Final repair and maintenance activities began on June 16 and were completed on June 20, 2008. The repair work involved site preparation, vegetation removal, geotextile placement, silt fence repair, the removal of existing plastic, riprap and gravel cobble mix placement, and the removal of existing gravel. The shoreline bank repair and maintenance work was performed in accordance with the May 29, 2009, scope of work described in the request for authorization approved on June 9, 2008, by EPA (ENSR 2008b; EPA 2008b). A complete summary of work performed is included in the Bankline Repair and Maintenance Activities Completion Report, Terminal 117, Port of Seattle (ENSR 2008a). 2.2.4 Independent cleanup actions in the Adjacent Streets and Residential Yards Study Area The City completed a series of independent cleanup actions between December 2004 and October 2005 (City of Seattle 2005) to reduce potential human exposure to PCB-impacted soil in the streets, ROWs, and yards in the vicinity of T-117 EAA (Map 2-68). These actions were conducted independently by the City without oversight under either MTCA or CERCLA. The independent cleanup actions are described in a site characterization data report (Integral 2006b) and briefly summarized below. Soil with PCB concentrations that exceeded 1 mg/kg was removed from residential yards at 8601 and 8609 17th Avenue S, the boat storage yard at 8603 Dallas Avenue S, and from along the west side of 16th Avenue S (Hart Crowser 2005). The action level of 1 mg/kg was based on MTCA's Method A cleanup level (CUL) for PCBs. The depth of soil removal was based on confirmation sampling .(King County and SPU 2005). A 100-ft section of the road shoulder on the north side of the 8500 block of Dallas Avenue S was paved to cover soil that contained PCB concentrations above 1 mg/kgimprove drainage. Shallow excavations (i.e., between 6 and 12 in.) and the placement of clean gravel were completed in the unpaved road shoulders along selected portions of Dallas Avenue S, between 14th Avenue S and 17th Avenue S; on 16th Avenue S, between Dallas Avenue S and S Cloverdale Street; and in a boat storage area located within the public ROW on Dallas Avenue S, between 14th Avenue S and 16th Avenue S. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 48 The City street ROWs surrounding the Basin Oil property bounded by Dallas Avenue S, 17th Avenue S, and S Donovan Street were graded and paved with asphalt. The existing catch basin located near the south driveway entrance to the T-117 Upland Study Area was cleaned, and a catch basin near 8609 17th Avenue S was removed. Basin Oil removed two catch basins and an oil/water separator on their property within the same time frame.Contaminated sediment was removed from three existing catch basins (located around the perimeter of the Basin Oil property); a catch basin near 8609 17th Avenue S was also removed. The existing catch basin in the boat storage yard was also cleaned. The following streets were pressure washed, and the existing catch basins serving those streets were cleaned: S Cloverdale Street, between 14th Avenue S and 16th Avenue S; S Donovan Street, between 16th Avenue S and 17th Avenue S; and in front of the building located at 8620 16th Avenue S. A temporary stormwater collection and treatment system was installed to capture runoff from the ROW independent cleanup action area. This work included the installation of the drainage features described above in Section 2.1.3.3, including five catch basins, two small pump stations, five 18,000-gal. storage tanks, and a temporary treatment system (i.e., settling followed by sand and granular activated-carbon filtration). All runoff from the area is now collected in the five storage tanks and released at a controlled rate to the City's CSS at 17th Avenue S and S Donovan Street. The temporary treatment system, associated with the storage tanks, was installed during the independent cleanup action to treat construction and post cleanup runoff and was removed in April 2005, when repeated sampling confirmed that PCBs were not detected in the incoming runoff. The City obtained discharge authorization from the County's Industrial Waste Program for this discharge. As part of the authorization, SPU tests the quality of water discharged to the CSS every month in which discharge occurs. The temporary stormwater collection system remains in place and will be maintained until removal action construction. 2.3 PREVIOUS ENVIRONMENTAL INVESTIGATIONS AND SUMMARY OF ENVIRONMENTAL DATA This section summarizes the chemistry data associated with the investigations presented in Table 2-1 2 for each study area of the T-117 EAA and the two RAAs. These investigations and other milestones are also presented on the timeline (Figure 1-1). Map 2-9 7 presents an overview of the sampling locations in all three study areas of the T-117 EAA. Data summarized in this section are presented along with screening levels (SLs) discussed in Section 3, where they are used to identify COPCs. PCBs, PAHs, and TPH are the most prevalent chemicals that exceed their respective the SLs in soil and Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 49 sediment within the T--117 EAA. The large quantity of data for the T-117 EAA indicates that the current environmental conditions at the site are likely the result of historical site use and operations. All available data are presented in Appendix C. However, not all samples are representative of current conditions as a result of previous removal actions (described in Section 2.2) and subsequent sampling results (i.e., MIS) that has superseded previous sampling results. Numbers of samples provided in this section are for only the actual field samples and do not include the quality assurance/quality control (QA/QC) samples (i.e., field duplicates and triplicates and laboratory duplicates). Maps and analytical results presented in the following sections present mean concentrations that include the results of QA samples. In addition, multiple samples may have been collected from a single location if samples were collected from multiple depth intervals at that location. A complete description of all the data management rules used in this step is provided in Appendix D. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 50 Table 2-21. Summary of previous investigations at T-117 Early Action Area No. of Samples from the T-117 EAA and Vicinity Used a Activity Date Summary Analyses in the EE/CA Source Summary of T-117 Historical Investigations Data Ttoo Oold or Nnot Aapplicable for Uuse in EE/CA Water and sediment samples were collected from the LDW, roadway Metro inspection ponding area, catch basin 5 outfall, and an apparent groundwater seep at sampling of the shoreline. PCBs, PAHs, and metals were detected in one or more of PCBs, PAHs, and URS roadway ponding 1984 the water and sediment samples. No PCBs were detected in the seep na metals (1994) area and sample. The ponding area was reportedly receivedused for non-contact shoreline seep cooling water during the period that the asphalt plant operated.discounted by subsequent investigators. Ecology sediment Sediment samples were collected from an onsite drainage ditch. Results 1985 and URS sampling and showed elevated concentrations of lead (1,666 mg/kg), arsenic (2,027 metals na 1986 (1994) inspections mg/kg), and zinc (5,416 mg/kg). Samples were collected from a waste oil tank and another tank that contained usable light oils. No PCBs were detected. However, total PCB and EPA TSCA URS 1989 halogenated hydrocarbons (as total chlorine) were reportedly detected at halogenated na inspection (1994) levels up to 1,160 mg/kg in the sampled product. No materials were noted hydrocarbons at the facility to qualify for PCB regulation. One surface sediment sample was collected at the toe of the bank. Onsite and offsite soil, sediment, groundwater, and surface water were sampled. Malarkey site PCBs and PAHs were detected in soil at the former ponding/waste areas. URS 1994 PCBs and PAHs na inspection Three monitoring wells and a groundwater seep were also sampled. PCBs (1994) were detected in all wells, and PAHs were detected in MW-03. PCBs were not detected in the seep sample. An asbestos-containing material survey was conducted. Twelve suspect EMCON Asbestos survey March 1996 asbestos na materials were found to contain detectable amounts of asbestos. (1996) Sediment Study Area Sediment Duwamish metals, PCB Waterway Exponent 1997 Site-wide LDW surface and subsurface sediment samples Aroclors, and 4 Phase 1 site (1998) SVOCs characterization Table 2-12. Summary of previous investigations at Terminal-117 Early Action Area (cont.) No. of Samples from the T-117 EAA and Vicinity Used a Activity Date Summary Analyses in the EE/CA Source PCB Aroclors, Duwamish selected PCB Waterway congeners, and NOAA sediment 1997 Site-wide LDW surface and subsurface sediment samples 3 total (1998) characterization polychlorinated study terphenyls metals, pesticides, PCB Aroclors and EPA site selected PCB Weston inspection: Lower 1998 Site-wide LDW surface and subsurface sediment samples 5 congeners, dioxins (1999) Duwamish River and furans, TBT, SVOCs, and VOCs Site-wide LDW chemical analyses of benthic invertebrate and clam tissue metals, SVOCs, Windward LDW RI Benthic 2004 2 samples and co-located sediment samples and PCB Aroclors, (2005a) Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 52 Table 2-12. Summary of previous investigations at Terminal-117 Early Action Area (cont.) No. of Samples from the T-117 EAA and Vicinity Used a Activity Date Summary Analyses in the EE/CA Source An initial sediment investigation was conducted to determine the nature metals, PCB Windward December and extent of contamination in the T-117 EAA. All surface and subsurface Aroclors, SVOCs, 137 et al. 2003 sediment were analyzed for PCBs and select locations were also VOCs, TBT (2005b) analyzed for SMS chemicals and TBT. Additional subsurface and surface sediment samples were collected from Windward the northern portion of T-117 to further refine the removal boundary. Large March 2004 PCB Aroclors 12 et al. asphalt deposits and other major debris located in the shoreline bank (2005b) were identified, described, and mapped. Surface sediment samples collected outside the offshore northern portion of the preliminary sediment boundary in the 2005 EE/CA were analyzed metals, PCB Windward June 2004 for PCBs, and archived samples collected in December 2003 that were Aroclors, SVOCs, 8 et al. either outside of the boundary or below the vertical extent of PCB and VOCs (2005b) T-117 EAA contamination were analyzed for all other SMS chemicals. investigation Surface and subsurface samples were collected in the northern portion of the site that extends into the proposed Marina dredge area. This sampling metals, pesticides, September Windward event was conducted to satisfy both the EPA T-117 EAA boundary PCB Aroclors, 12 2004 (2005a) definition and the PSDDA sediment characterization requirements for the SVOCs, and VOCs Marina. Surface sediment samples collected near the proposed sediment boundary for the 2008 EE/CA were analyzed for dioxins and furans and PCB Aroclors, Windward PCBs to determine if there were any dioxin/furan TEQ exceedances August dioxins and furans, and outside of the boundary and to refine the extent of the sediment removal 18 2008 mercury and Integral boundary presented in this EE/CA. Two surface sediment samples were dieldrin (2009) also collected for mercury and dieldrin to evaluate potential soil to sediment contamination from the Marina. T-117 Upland Study Area - Soil Work included review of Ecology and Malarkey Asphalt files, installation of three monitoring wells (MW-01, MW-02, and MW-03), soil sampling and Ecology site metals, total PCBs, analysis of borehole samples, groundwater sampling, sampling of product Parametrix hazard May 1991 pesticides, 8 in USTs and ASTs. Metals, PCBs, pesticides, and VOCs were found in (1991) assessment SVOCs, VOCs soil. Results of TCLP analyses on soil were below dangerous waste criteria. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 53 Table 2-12. Summary of previous investigations at Terminal-117 Early Action Area (cont.) No. of Samples from the T-117 EAA and Vicinity Used a Activity Date Summary Analyses in the EE/CA Source UST Four USTs containing diesel and waste oil were decommissioned, Hart decommissioning including a partially buried railroad tank car. Three USTs were closed in 1992 TPH 6 Crowser and site place by filling with concrete slurry. The railroad tank car was removed. (1992) assessment Soil samples were taken from the tanks and tested for TPH. One surface sediment sample was collected at the toe of the bank. Onsite and offsite soil, sediment, groundwater, and surface water were sampled. Malarkey Asphalt PCBs and PAHs were detected in soil at the former ponding/waste areas. total PCBs and URS Company site 1994 na Three monitoring wells and a groundwater seep were also sampled. PCBs PAHs (1994) inspection were detected in all wells, and PAHs were detected in MW-03. PCBs were not detected in the seep sample. Soil and water September Surface soil samples were collected from locations near the ponding area, EMCON total PCBs 7 sampling 1995 former railroad tank car, and storm drain ditches. (1996) Focused site Surface soil samples were collected from locations near the ponding area total PCBs, PAHs, SECOR July 1997 55 characterization and former railroad tank car to delineate the extent of contamination. and TPH (1998) Windward Utility corridor soil October Three borehole locations were sampled along a utility alignment that PCB Aroclors 3 and Onsite sampling 1999 extended from the former tank area to the south building. (2004) Actions included the removal and treatment of impounded stormwater, the PCB soil removal October excavation and disposal of over 2,000 tons of PCB-contaminated soil with and containment 1999 to concentrations ranging up to 500 mg/kg, backfilling, installation of a Onsite total PCBs 14 roadway area February pavement cap, and storm drain improvements. Also included was the (2000a) (1999 TCRA) 2000 abandonment of the large-diameter well and replacement of three monitoring wells. PCB removal action target level in soil was 25 mg/kg. Underground A 375-gal. (1,420-L) non-leaking diesel tank was removed. Two soil January Onsite diesel storage samples from excavation indicated elevated TPH diesel levels (462 and TPH 2 2000 (2000b) tank removal 2,780 mg/kg). Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 54 Table 2-12. Summary of previous investigations at Terminal-117 Early Action Area (cont.) No. of Samples from the T-117 EAA and Vicinity Used a Activity Date Summary Analyses in the EE/CA Source Soil samples were collected from the top of the shoreline, the southern metals, PCB Windward December drainage ditch, and the adjacent Dallas Avenue S roadway area. Solid Aroclors, and 40 et al. 2003 samples were collected from catch basins. PCBs were detected in most SVOCs (2005b) soil samples. To better define the extent of contamination, shallow soil borings were T-117 EAA collected from the northern upland bank. All these samples were analyzed investigations for PCBs and compared to SMS to assess the risk from potential erosion. Soil sampling was also conducted to estimate concentrations of PCBs in Windward March 2004 the roadway along the entrance area of the T-117 property and determine PCB Aroclors 16 et al. if these materials were the likely source of elevated PCBs in and around (2005b) catch basin 5. Roadway soil samples and catch basin samples were analyzed for PCBs. Large asphalt deposits and other major debris located in the south ditch were identified, described, and mapped. Four shallow soil grab samples were obtained from the concrete-enclosed soil-filled planter areas at the north side of the south building at T-117. T-117 South November PCB concentrations in the four soil samples ranged from 0.03 to 0.22 Onsite building planter PCB Aroclors 4 2004 mg/kg. Soil in the west planter was subsequently covered over with a (2004) soil sampling layer of clean gravel. Soil in the east planter was covered with asphalt pavement. This work was performed as part of an iterative process to provide additional information on the nature and extent of PCBs in soil. Windward T-117 Upland soil Subsurface soil samples were collected from three upland regions of TJune 2005 PCB Aroclors 95 et al. sampling 117: the unpaved upland area along the northern shoreline; beneath the (2005d) pavement along the shoreline edge of the site; and the ditch along the southern boundary of the site. Supplemental upland soil sampling was conducted from 26 soil borings (0 to 9 ft).Three soil samples (SB-26, SB-51, and SB-28) along the northern shoreline contained PCB concentrations similar to those of the previous T-117 Upland soil upland sampling effort in the same area. Two soil samples located in the Windward August sampling - paved driveway area inboard of the bank extending north of the 1999 PCB PCB Aroclors 89 et al. 2005 supplemental removal area had two of the highest PCB concentrations (1,200 and (2005e) 730 mg/kg for soil samples SB-30 and SB-50, respectively). These data identified a new area of elevated PCB contamination on the T-117 EAA not previously observed in the June 2005 soil sample results. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 55 Table 2-12. Summary of previous investigations at Terminal-117 Early Action Area (cont.) No. of Samples from the T-117 EAA and Vicinity Used a Activity Date Summary Analyses in the EE/CA Source PCB Aroclors, Soil borings were collected throughout the upland property. PCBs were Windward T-117 Upland January metals SVOCs, detected in several samples. The results of this investigation led to the 230 and DOF Investigation 2006 pesticides and 2006 TCRA for PCB contaminated soil. (2006) TPH Confirmation samples were collected in the TCRA excavation areas upon T-117 TCRA October to completion of the soil removal activities. Baseline samples were also PCB Aroclors and RETEC activities (2006 November 79 collected in the roadway along Dallas Avenue S before and after the TPH (2007b) TCRA) 2006 TCRA. Subsurface Soil samples were collected to determine the presence and Windward PCB Aroclors, T-117 EAA dioxin August concentrations of dioxins and furans in the T-117 Upland Study Area. and PAHs, TPH, and 29 investigation 2008 Select subsurface samples were also analyzed for TPH and PCBs to Integral dioxins and furans further refine the vertical extent of the removal boundary. (2009) Adjacent Streets and Residential Yards Study Area Soil samples were collected of right-of-wayROW street dust and from Integral Street dust and storm drain catch basins by Seattle Public UtilitiesSPU and King County (2006b) 2004 PCB Aroclors and soil ROW Health Department and analyzed for PBCBs. Catch basin sample CB41 31 Integral 2005 dioxin and furans sampling and street dust sample SD52 were analyzed for dioxins that led to (2008b)(20 discovery of dioxin/furans in this area.. 08) Subsurface soil samples were collected from boreholes and test pits Subsurface soil 2004 Integral within the ROW by Seattle Public UtilitiesSPU and King County Health PCB Aroclors 118 ROW sampling 2005 (2006) Department. 2004 Samples were collected from yards adjacent to the ROW by Seattle Public Integral Yard soil sampling PCB Aroclors 97 2005 UtilitiesSPU and King County Health Department. (2006) In June 2005, SPU collected confirmatory soil samples at the base of the 56 Hart excavation following the removal of PCB-contaminated soil from the Yard soil sampling 2005 PCB Aroclors (not included in Crowser residential lots adjacent to the impacted ROW. All confirmation samples Appendix C) (2005) were below 1 mg/kg. Twenty-five direct push borings were advanced up to a depth of 20 ft bgs Subsurface February PCB Aroclors, to delineate the extent of PCB contamination and to screen for other Integral sampling in and March TPH, PAHs, 83 COPCs within the Adjacent Streets. Results of the investigation were (2006b) Adjacent Streets 2006 BTEX, and metals used to delineate the preliminary boundary for the Adjacent Streets. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 56 Table 2-12. Summary of previous investigations at Terminal-117 Early Action Area (cont.) No. of Samples from the T-117 EAA and Vicinity Used a Activity Date Summary Analyses in the EE/CA Source Surface and subsurface soil samples were collected to determine the Windward T-117 EAA dioxin August PCB Aroclors and presence and concentrations of PCBs and dioxins and furans in the 85 et al. investigation 2008 dioxin and furans Adjacent Streets and Residential Yards Study Area. (2009) Soil samples were collected from the adjacent streets and right-of- PCB boundary waysROWs as part of the PCB boundary refinement investigation. The April and Integral refinement samples consisted of direct push borings in the streets and right-of- PCB Aroclors 76 July 2009 (2009) Adjacent Streets waysROWs, discrete parking strip samples, and multi-increment samples (MIS) from right-of-waysROWs. PCB boundary April and MIS soil samples were collected from residential yards as part of the PCB Integral refinement PCB Aroclors 75 July 2009 boundary refinement investigation. (2009) Residential Yards Ecology analyzed MIS sample splits for dioxins and furans from the MIS Dioxin analysis Ecology July 2009 samples from Adjacent Streets during the PCB bBoundary rRefinement dDioxin and furans 9 Adjacent Streets (2009) iInvestigation as described above. Ecology analyzed MIS sample splits for dioxins and furans from the MIS Dioxin analysis dDioxins and Ecology July 2009 samples from Residential Yards during the PCB bBoundary rRefinement 24 Residential Yards furans (2009) iInvestigation as described above. Groundwater Monitoring (2003 to -2008) Groundwater was sampled from three wells in the vicinity of T-117. TPH-D Groundwater ([0.70 mg/L)], TPH-O ([1.4 mg/L)], and six PAH compounds (at PCB Aroclors, Onsite sampling at T-117 May 2003 5 concentrations ranging from 0.013 to 1.6 g/L) were detected in MW-03. PAHs, and TPH (2003) wells PCBs were not detected in any of the wells. T-117 EAA PCB Aroclors, Windward December Water samples were collected from intertidal seeps. Copper, zinc, and investigation SVOCs, VOCs, 5 et al. 2003 BEHP were detected in seep samples. seeps metals (2005b) T-117 EAA Windward January Water samples were collected from groundwater monitoring wells. No PCB Aroclors, investigation 5 et al. 2004 chemicals were detected in the monitoring well samples. PAHs, VOCs monitoring wells (2005b) Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 57 Table 2-12. Summary of previous investigations at Terminal-117 Early Action Area (cont.) No. of Samples from the T-117 EAA and Vicinity Used a Activity Date Summary Analyses in the EE/CA Source Two new groundwater monitoring wells were installed to extend the existing network northward. All shoreline monitoring wells and upgradient Windward T-117 Upland PCB Aroclors, June 2005 monitoring well (MW) 3 were analyzed for PCBs also monitored for the 6 et al. groundwater PAHs, and TPH presence of free product. One well was also analyzed for PAHs and TPH. (2005d) PCBs were detected in one well. Windward T-117 Upland January One well was sampled for PCBs to verify the detection noted in the PCB Aroclors 1 and DOF Investigation 2006 previous event (2006) PCB Aroclors, ENSR | T-117 Upland August Groundwater in was collected prior to 2006 TCRA activities metals, PCBs, and 7 AECOM groundwater 2006 TPH (2008) T-117 EAA 5 new monitoring wells were installed in the T-117 EAA. Two wells were PCB Aroclors, ENSR | Groundwater installed along Dallas Avenue S downgradient of Basin Ooil and the other March 2008 SVOCs, VOCs, 11 AECOM Monitoring three wells were installed along the T-117 shore line as replacement wells metals (2008) 2008 1st Event for the ones removed during the 2006 TCRA. T-117 EAA TSS, TPH, metals, ENSR | Groundwater BTEX, PCB June 2008 Groundwater samples were collected. 10 AECOM Monitoring Aroclors, SVOCs, (2008) 2008 2nd Event VOCs, and PAHs T-117 EAA TSS, TPH, metals, ENSR | Groundwater September Groundwater samples were collected. Installed one new upgradient BTEX, PCB 10 AECOM Monitoring 2008 monitoring well in the T-117 EAA (MW-11). Aroclors, SVOCs, (2008) 2008 3rd Event VOCs, and PAHs TSS, TPH, metals, T-117 EAA BTEX, PCB ENSR | Groundwater December Groundwater samples were collected. Aroclors, SVOCs, 11 AECOM Monitoring 2008 VOCs, PAHs, and (2008) 2008 4th Event dioxins and furans T-117 EAA TSS, TPH, metals, Groundwater BTEX, PCB AECOM March 2009 Groundwater samples were collected. 13 Monitoring Aroclors, SVOCs, (2009a) 2009 1st Event VOCs, and PAHs Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 58 Table 2-12. Summary of previous investigations at Terminal-117 Early Action Area (cont.) No. of Samples from the T-117 EAA and Vicinity Used a Activity Date Summary Analyses in the EE/CA Source Groundwater samples were collected. Modified the groundwater T-117 EAA TSS, TPH, metals, monitoring program at the T-117-Upland Study Area. The Department of Groundwater PCB Aroclors, AECOM May 2009 Ecology installed two new monitoring wells upgradient of Basin Oil (MW- 7 Monitoring SVOCs, and (2009b) 12 and MW-13). These wells will be adopted into the T-117 EAA 2009 2nd Event cPAHs monitoring well net work in subsequent groundwater sampling events. T-117 EAA TSS, TPH, metals, Groundwater August PCB Aroclors, AECOM Groundwater samples were collected. 10 Monitoring 2009 SVOCs, VOCs, (2009c) 2009 3rd Event and cPAHs a Numbers of samples in this table are for only the actual field samples and do not include the QA/QC samples (e.g., field duplicates). In addition, multiple samples may have been collected from a single location if samples were collected from multiple depth intervals at that location. AST aboveground storage tank MTCA Model Toxics Control Act SPU Seattle Public Utilities BBP benzyl butyl phthalate MIS multi-increment sampling SQS sediment quality standards BEHP bis(2-ethylhexyl) phthalate NOAA National Oceanic and Atmospheric Administration SVOC semivolatile organic compound bgs below ground surface PAH polycyclic aromatic hydrocarbon T-117 Terminal 117 BTEX benzene, toluene, ethylbenzene, and xylene PCB polychlorinated biphenyl TBT tributyltin COPC contaminant of potential concern PCP pentachlorophenol TCLP toxicity characteristic leaching procedure CSL cleanup screening level PSDDA Puget Sound Dredged Disposal Analysis TCRA time-critical removal action DOF Dalton, Olmsted & Fuglevand ROW right-of-way TPH total petroleum hydrocarbons EAA early action area Marina South Park Marina TSCA Toxic Substances Control Act Ecology Washington State Department of Ecology NOAA National Oceanic and Atmospheric Administration TSS total suspended solids LDW Lower Duwamish Waterway QA/QC quality assurance/quality control UST underground storage tank Marina South Park Marina SMS Washington State Sediment Management Standards VOC volatile organic compound Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 59 2.3.1 T-117 Sediment Study Area Extensive sediment sampling in the T-117 EAA was conducted from 1998 to 2008. Most of the investigations focused on PCBs; however, additional chemicals analyzed included PAHs, other semivolatile organic compounds (SVOCs), pesticides, dioxin and furans, VOCs, and metals, including tributyltin (TBT). Appendix C includes a complete list of available data for each chemical analyzed in the T-117 Sediment Study Area. 2.3.1.1 PCBs One hundred and eighty-two surface and subsurface sediment samples were analyzed for PCBs. PCB concentrations for surface grab samples are presented on Map 2-108, and concentrations for subsurface samples are presented on Map 2-119. PCB concentrations on both maps are compared to Washington State Sediment Management Standards (SMS) criteria. The detected PCB concentrations in surface sediment ranged from 1.9 to 2,200 g/kg organic carbon (OC), and the detected PCB concentrations in subsurface sediment ranged from 1.4 to 2,600 g/kg OC. Both the surface and subsurface sediment sampling data indicate a spatial trend of PCB concentrations decreasing from the bank out towards the navigation channel. The highest PCB concentrations were collected from within 100 horizontal ft of the shoreline bank and were typically confined to the upper 1 to 2 ft of sediment in the nearshore cores. PCB concentrations were also generally higher in the northern portion of the T-117 EAA (as opposed to the southern portion), at similar depths. This trend suggests the presence of a historical and ongoing upland source for these chemicals, which were subsequently conveyed to the river via stormwater runoff and direct erosion from the T-117 Upland Study Area and shoreline bank. Map 2-8 also identifies historical sampling locations that have since been re-occupied by more recent sampling locations. The more recent samples are considered to be more representative of current site conditions. 2.3.1.2 PAHs Thirty-four surface and subsurface sediment samples were analyzed for PAHs. PAH data show that several individual PAHs and total carcinogenic PAH (cPAH) TEQ had maximum concentrations that exceeded their respective SLs. Less than 10% of the samples analyzed had PAH concentrations that exceeded the SL. These samples were collected from the toe of the shoreline bank and were co-located with samples that had PCB exceedances. The detailed results (Appendix C) show that PAHs were detected in 3 of 34 samples at concentrations that exceeded the SL. Two of these samples were from surface sediment sampling locations (25-G and 37-G), and one was from a subsurface sampling location (25-SC). These locations are shown on Map 2-1210. The surface sediment sample from 25-G exceeded the sediment quality standards (SQS) for three Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 60 individual PAHs, and the sample from 37-G had 13 individual PAH SQS exceedances. Total high-molecular-weight PAHs (HPAHs) also exceeded the SQS in 37-G, and total low-molecular-weight PAHs (LPAHs) in this sample exceeded both the SQS and cleanup screening level (CSL). The one subsurface sampling location, 25-SC, had one individual PAH (acenaphthene) concentration that exceeded the SL in the 2-to-4-ft depth interval. 2.3.1.3 Other SVOCs and VOCs Thirty-three surface and subsurface sediment samples were analyzed for other SVOCs. SVOCs that exceeded SMS were relatively few as compared with the PCB exceedances and were in discrete locations, as shown on Map 2-120. The following SVOCs exceeded their SL: bis(2-ethylhexyl) phthalate (BEHP) and butyl benzyl phthalate (BBP) (at DR206); hexachlorobenzene (at R19); phenol; (at C10-1, C10-2, and DR 207); and benzyl alcohol (at 08-G). VOCs were not detected in any sediment sample analyzed. 2.3.1.4 Metals Thirty-one two sediment samples were analyzed for metals. Arsenic was the only metal that exceeded its SL. Detected concentrations of aArsenic ranged from 7 to 22 mg/kg. Map 2-120 shows the locations of all samples analyzed for the full suite of SMS chemicals, which included metals. 2.3.1.5 Dioxins and Furans Eight surface sediment samples were analyzed for dioxins and furans. These samples were collected to provide an initial indication of whether the dioxins and furans were present in the sediment and if dioxin/furan TEQs were greater than theits SL (4.5 ng/kg) at locations where PCB concentrations were below theits SL for PCBs; therefore,. no dioxin and furan analyses were performed for samples collected from sediment areas that had elevated PCB concentrations and were thus targeted for removal. The dioxin/furan TEQs ranged from 2.11 to 9.36 ng/kg and are shown on Map 2-113. 2.3.2 T-117 Upland Study Area Soil conditions at the T-117 Upland Area have been determined through the evaluation of an extensive collection of soil samples from borings advanced from 1990 to 2008. Chemicals analyzed included PCBs, TPH, PAHs, other SVOCs (including phthalates, and phenols), pesticides, and metals. As a result of the 1999 and 2006 TCRAs, 5,200 tons of contaminated soil were removed from the Upland T-117 Area. All available soil data (including data for samples collected from soil that is remaining or has been excavated) for the T-117 Upland Study Area are provided in Appendix C. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 61 2.3.2.1 PCBs A total of 682 samples from 282 locations have been analyzed from the T-117 Upland Area for PCBs. During the two TCRAs, the soil associated with 83 sampling locations was excavated, leaving 539 samples that are representative of current site conditions. PCB concentrations are presented by both subarea (A through F) and by depth range (0 to -7 ft, 7 to -12 ft, and >15 ft) to facilitate data presentation because of the large number of sampling locations in the T-117 Upland Study Area. Subareas were delineated during the 2006 T-117 Upland Investigation (Windward and DOF 2006) and are shown on Map 2-124. PCB concentrations associated with both remaining and excavated soil in the T-117 Upland Study Area are presented on Maps 2-153a through 2-153c by depth. Maps 2-146 through 2-20 18 present the PCB sample concentrations associated with the remaining and excavated T-117 Upland Study Area soil by subarea (A through F). The excavated data representing excavated soil are presented to illustrate chemical distribution and to facilitate the assessment of data gaps. PCBs (predominantly Aroclor 1260) are generally found within the uppermost 2 ft of surface soil, and concentrations tend to decrease with depth (Maps 2-153a through 2-153c). Exceptions to this trend have been found at the following locations: Beneath the 1999 TCRA removal area (Subarea C, Map 2-168) and the 2006 TCRA removal area (Subarea B, Map 2-157), where the highest PCB concentrations were located at 2 to 8 ft bgs and then decreased with depth Near Catch Basin 5 (Subarea E, Map 2-1820), where elevated PCB concentrations ranged from 0 to 6.5 ft in depth The highest remaining PCB concentrations (i.e., greater than 1,000 mg/kg) were detected in the upper 2 ft at location T-117-D-11 and between 2 and 5 ft bgs at location T-117-E-1. Below 7 ft, PCBs were detected above 50 mg/kg only at locations PS-7 (110 mg/kg) and T-117-6 (94 mg/kg). The 2006 TCRA included the excavation of three areas in Subarea B (Map 2-157) that contained the highest concentrations of PCBs in the T-117 Upland Area, including the highest PCB concentration (9,200 mg/kg) at location T-117-B-8. 2.3.2.2 TPH A total of 377 samples have been analyzed for TPH from 162 locations. Of this total, 37 sampling locations were associated with the soil that was excavated during the 1999 and 2006 TCRAs. The site-wide total TPH chemical concentrations associated with samples that were collected from the remaining and excavated soil in the T-117 Upland Area are presented on Maps 2-1921a through 2-1921c. Maps 2-220 through 2-264 present total TPH chemical concentrations associated with samples that were collected from the remaining and excavated soil in the T-117 Upland Area by subareas (A through F). Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 62 The highest concentrations of TPH (i.e., greater than 10,000 mg/kg) were detected in the former roadway ponding area (Subarea C, Map 2-242) and in the vicinity of Catch Basin 5 (Subarea E, Map 2-246), where elevated TPH concentrations were detected as deep as 6.5 ft. Most of the shallow soil (0 to 2 ft bgs) that had elevated concentrations of TPH was removed as part of the 1999 and 2006 TCRAs (Maps 2-213 and 2-2432). 2.3.2.3 PAHs A total of 303 samples from 81 locations have been analyzed, and soil associated with 35 of these sampling locations was excavated during the 1999 and 2006 TCRAs. Individual cPAH compounds were compared with SLs as total cPAH TEQ.5 Twentyone percent of soil samples exceeded the SL for total cPAH TEQ. A summary of the T- 117 Upland Study Area soil cPAH concentrations associated with soil that has since been excavated are presented on Maps 2-275 and 2-286. cPAHs tended to be co-located with elevated concentrations of PCBs and TPH. The highest cPAH TEQ concentrations were detected at T-117-D-6 (22.67 mg/kg), T-117-B-4 (23.82 mg/kg), E-1 (27.89 mg/kg) and T-117-C-4 (176.3 mg/kg). Three of these samples were collected from between 2 and 5 ft bgs. 2.3.2.4 Other SVOCs and VOCs A total of 303 samples have been analyzed from 81 locations, and soil associated with 35 sampling locations was excavated during the 1999 and 2006 TCRA. These chemicals had maximum concentrations below comparative SLs. SVOC concentrations (including PAHs) for samples collected within the T-117 Upland Area are presented in Appendix C. 2.3.2.5 Metals A total of 141 samples from 42 locations have been analyzed for metals. Metals have been detected in the T-117 Upland Area, but only arsenic exceeded the SL. The highest arsenic concentrations were detected at locations T-117-C-8 (55 mg/kg), T-117-D-6 (40 mg/kg), and T-117-D-10 (160 mg/kg), as shown on Map 2-297. All of the samples were collected from within the upper 4 ft. Concentrations of PCBs and TPH were also elevated at these sampling locations. 2.3.2.6 Dioxins and Furans A total of 21 samples from eight locations were analyzed for dioxins and furans. All samples contained detected concentrations of one or more dioxin or furan congeners. These concentrations, expressed as dioxin/furan TEQs, ranged from 0.272 to 296 ng/kg and are shown on Map 2-2830. 5 cPAH TEQ benzo[a]pyrene equivalents were calculated in accordance with Ecology's calculation guidance (WAC 173-340-900 Table 708-2). Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 63 2.3.3 Adjacent Streets and Residential Yards Study Area Between 2004 and 2009, several investigations were conducted within the Adjacent Streets to support the City's site characterization and independent cleanup actions (Integral 2006b) and in the Adjacent Streets and Residential Yards Study Area to support boundary refinement activities completed since the Adjacent Streets were included in the T-117 EAA in 2007 (Integral 2009; Windward and Integral 2009). Samples collected prior to 2008 were generally single samples collected from surface soil, test pits, borings, street dust, and catch basins. The detection of PCBs and dioxins and furans in Residential Yards samples collected in 2008 led EPA to direct the City to conduct additional sampling using MIS in 2009. An MIS sample is a composite of small amounts of soil (soil increments) collected at many locations (30 to 44 individual soil aliquots or increments for this study) from a decision unit (DU); the laboratory analysis is performed on a sub-sample from the composite sample. A DU is a defined area for which a characterization or a decision is to be made; for example, a DU can represent an exposure unit and/or a remediation unit. A MIS sample provides a single analytical result for each DU; that result represents an estimate of the average concentration within the DU, but provides no information on the variability (numerical or spatial) of concentrations across the DU. DUs were delineated collaboratively with EPA based on the objective of providing an average chemical concentration for soil in the DU (Integral 2009). MIS samples were collected from the surface depth interval (0.0 to 0.2 ft [0.0 to 2.0 in.]) and the subsurface depth interval (0.2 to 0.5 ft [2.0 to 6.0 in.]). Where grass was present, the surface interval began below the grass roots. The MIS increments were aggregated to form a single composite to provide an average chemical concentration for soil in a given DU (Integral 2009). MIS sampling was conducted in two phases during 2009. Residential Yard DUs were delineated in consideration of the potential differences in how residents used their yards (potential exposures), possible differences in the soil disturbance histories of portions of yards (e.g., front versus back yards), the potential for contamination in streets to enter yards (e.g., trackout, runoff, and resuspended dusts), and the accessibility of surface soils. Residential Yard DUs for the first phase of sampling represented entire yards. In some cases, Residential Yard DUs for the second phase of sampling represented only the portions of Residential Yards adjacent to streets. EPA determined that results from previous investigations that were based on point samples located within the 2009 DU areas were to be superseded by results of the 2009 MIS sampling in those areas. Appendix C includes a complete list of available data for each chemical analyzed in the Adjacent Streets and Residential Yards Study Area. Appendix C also identifies samples that were removed during the City's independent cleanup actions or data that Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 64 were superseded by subsequent MIS composite sampling data; these data are presented to illustrate the current spatial distribution of contaminants. The SLs for soils discussed in the following sections are based on the MTCA Method B standard formula values for direct human contact, with the exception of lead, TPH, and PCBs. For lead and TPH, the soil SLs are based on the MTCA Method A unrestricted land use CULs. Method A provides the only applicable SLs for these chemicals. PCB SLs are based on the TSCA applicable or relevant and appropriate requirements (ARARs) (see Section 4.3.2.1). 2.3.3.1 Adjacent Streets This section summarizes the data obtained from soil investigations conducted within the Adjacent Streets between 2004 and 2009. Several investigations were conducted within the Adjacent Streets to support the City's site characterization and independent cleanup actions between 2004 and 2006 (Integral 2006b) and in the Adjacent Streets and neighboring residential properties to support boundary refinement activities completed since the Adjacent Streets were included in the NTCRA in 2007 (Integral 2009; Windward and Integral 2009). Appendix C includes a complete list of available data for each chemical analyzed in the Adjacent Streets. Appendix C also identifies samples that were removed during the City's independent cleanup actions or data that were superseded by subsequent MIS composite samples; these data are presented to illustrate the current spatial distribution of contaminants. PCBs A total of 382 367 soil, street dust (i.e., fine soil accumulated on street surfaces and shoulders), and catch basin solids and MIS samples were collected and analyzed for PCBs within the Adjacent Streets. Maps 2-29 and 2-30 show the locations where soil was sampled from 2004 through 2006 and 2008 through 2009, respectively. (Map 2- 31); tThe source materialcontaminated soil associated with 17 of these the 367 samples (i.e., 4 soil, 7 street dust, and 6 catch basin samples) was removed in conjunction with the City's independent interim cleanup actions of 2004 and 2005. Map 2-31 shows the locations of soil samples that were in areas where soil was subsequently removed as part of the City's 2004 and 2005 cleanup actions, or were superseded by subsequent sampling conducted by the City in 2008 and 2009. The sampling locations within the Adjacent Streets that had PCB concentrations greater than the SL (1 mg/kg; MTCA Method B/TSCA) were located on Dallas Avenue S, between 16th and 17th Avenues S, the north portion of 17th Avenue S, and in other isolated areas on Dallas Avenue S and S Donovan Street. The detected PCB concentrations in point samples ranged from 0.0025 mg/kg to 480 mg/kg at TP40 (located at 8601 17th Avenue S near the intersection with Dallas Avenue S). Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 65 PCBs were also detected at concentrations greater than 1 mg/kg were detected in street dust (e.g., upper 0.1 in. of soil) along S Cloverdale Street, along S Donovan Street near 17th Avenue S, and in street dust samples collected along Dallas Avenue S in conjunction with the 2006 TCRA at the T-117 Upland Study Area. PCB concentrations greater than 1 mg/kg, but less than 10 mg/kg, were generally detected only in the upper 12 in.1.0 ft of soil, although there were isolated exceedances in samples collected at depths of up to 2.0 ft. at locations P68, P83, P85, TP12, TP20, TP21, and TP41; and (at depths of up to 48 4.0 ft at locations MW10, P65, and P66. The specific depth intervals are presented on Map 2-28. PCB concentrations greater than 10 mg/kg were limited to surface samples (0-to-6-in. depth interval) in the immediate vicinity of the T-117 Upland Study Area, with the following exceptions: Ten exceedances in samples with depths ranging between 0.0 and 1.0 ft at 12 in. bgs (at locations P95, P100, TP6, TP8, TP9, TP12, TP13, TP19, TP26, and TP41 Five exceedances in samples with depths ranging between 0.0 and 2 ft bgs at 24 in. bgs (at locations P86, P100, TP9, TP19, and P81 MIS samples were collected from 12 decision units (DUs) in the Adjacent Streets. DUs were areas from which the MIS sample increments were aggregated to form a single composite MIS sample. DUs were delineated collaboratively with EPA based on the objective of providing an average chemical concentration for soil in the DU. MIS samples were collected from the surface (0.0-to-0.2-ft depth interval) and subsurface (0.2-to-0.5-ft depth interval). Where grass was present, the surface interval began below the grass roots. Total PCBs were detected in all samples at concentrations that ranged from 0.055 mg/kg at DU30 (0.2 to 0.5 ft bgs) to 8.1 mg/kg at DU19 (0.2 to 0.5 ft bgs) (Map 2-32)30). The second highest total PCB concentration was also detected at DU19 in the 0.0-to-0.2-ft interval (5.7 mg/kg). A total of 18four Adjacent Streets DUs had total PCB concentrations (expressed as means for locations with sample replicates) that exceededing 1 mg/kg total PCBs. There were no total PCB concentrations higher than exceedances of 1 mg/kg in DUs at the southern (south side of upper S Donovan Street) extent of the 2009 PCB investigation. Areas designated for cleanup are identified in Section 4. TPH A total of 53 63 soil, street dust, and catch basin samples were collected for the analysis of TPH within the Adjacent Streets (Map 2-3432). The contaminated soil associated with seven of these samples (i.e., one soil sample from TP48, two soil samples from TP49, street dust samples from SD20 and SD18, and catch basin samples from SD8 and CB1-DAL) was removed in conjunction with the City's independent 2004 and 2005 cleanup actions. The source material (catch basin solids) associated with four of these samples (SD3, SD8, SD20, and RCB101) was removed in conjunction with the City's independent cleanup actions. TPH-D exceeded the SL (2,000 mg/kg; [MTCA Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 66 Method A soils for unrestricted land use]) at two locations a catch basin located at the corner of Dallas Avenue S and S Donovan Street (SD3) and a five-point surface composite soil sample from the ROW area at the east end of S Donovan Street (SD4) that was previously used by Basin Oil to store equipment. TPH-O exceeded 2,000 mg/kg in eight samples, including two catch basins (SD3 and SD8), five street dust samples (SD2, SD4, SD7, SD19, and SD21), and one push probe location (P81). TPH analyses of street dust and catch basin samples showed that of the four samples collected to the west of 14th Avenue S (SD27, SD28, SD29, and SD30), none exceeded the comparative criteriaSL for TPH-D (2,000 mg/kg). TPH-O exceeded the comparative criteriaSL of 2,000 mg/kg at one of the four sampling locations, a catch basin located at the southwest corner of S Donovan Street and 12th Avenue S (SD30). The data for tThese six four sampling locations are located outside of the Adjacent Streets boundary and therefore are not shown on Map 2-34 32 but are presented in Appendix C. PAHs A total of 12 soil and street dust samples from within the Adjacent Streets Area were analyzed for PAHs; two samples (SD8 and RCB101CB1-DAL) were collected from soil that was subsequently removed in conjunction with the City's independent cleanup actions. Total cPAH TEQs associated with both the remaining and excavated Adjacent Streets soil are presented on Map 2-35.33. At five locations (MW-12 [two intervals], P60, P81, and SW1-Tank), total cPAH TEQs exceeded the SL (0.14 mg/kg; [MTCA Method B]). The highest cPAH TEQ was detected at MW-12 (320 mg/kg in the, 0.0- to- 60.5-ft in. depth bgsinterval). cPAHs were detected at P60, located on Dallas Avenue S (west of 16th Avenue S), where total Total cPAHs were detected in the 4-to-6-ft depth interval at P60, located on Dallas Avenue S (west of 16th Avenue S) in the 4-to-6-ft depth interval, and appeared to be associated with in a thin soil horizon between 5 and 5.5 ft bgs. At P81, located near the east end of S Donovan Street, total cPAHs were detected in the 21-to-42-ft depth interval. The individual cPAHs chrysene, dibenz(a,h)anthracene, and indeno(1,2,3-cd)pyrene, were also detected at concentrations greater than the SL at these sample locations and intervals (see Appendix C). Other SVOCs and VOCs Seven samples were collected from five locations within the Adjacent Streets (MW11, MW-12, MW-13, P72, and P78) for benzene, toluene, ethylbenzene, and xylene (BTEX) analyses. Benzene was detected at a MW-12 in two different intervals (0.0082 mg/kg at 0 to 6 in. bgs and 0.0019 mg/kg at 2.5 ft bgs). Toluene was detected at three locations (MW12, P72, and P78), with the highest concentration (11 mg/kg) at P78 on Dallas Avenue S, between 17th Avenue S and S Donovan Street (east of Basin Oil). Phthalate esters, including BEHP, were detected in two street dust and catch basin samples. Concentrations of BEHP ranged from 0.79 mg/kg to 6.2 mg/kg (SW1-Tank). Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 67 In addition, there were detections of other miscellaneous SVOCs (4_methylphenol, and phenol) and VOCs (2-butanone, carbazole, and carbon disulfide) in street dust and catch basin samples (see Appendix C). Metals A total of 19 soil and catch basin/street dust samples from within the Adjacent Streets were analyzed for metals. The soil from one two of these locations (SD8 and CB1-- DAL) was removed in conjunction with the City's independent cleanup actions. Arsenic was the only metal that exceeded its SL (0.67 mg/kg; [MTCA Method B/TSCA]), which occurred at two all locations (MW-12 and P81; Map 2-36). Arsenic was detected at varying depth intervals in 8 of the 19 soil and catch basin/street dust samples analyzed (see Map 2-34 and Appendix C). Arsenic was not detected in the remaining 11 samples; however, the arsenic reporting limits for these samples were all greater than the SL. Arsenic concentrations associated with both the remaining and excavated Adjacent Streets soil are presented on Map 2--3634. Dioxins and Furans Archived samples collected in 2004-2005 from catch basins, manholes, and street dust as part of the City's source-tracing program for the LDW (Herrera 2004) were later selected for the analysis of dioxins and furans. The samples included one street dust sample (SD52) collected at the intersection of Dallas Avenue S and 16th Avenue S (within the Adjacent Streets portion of the T-117 EAA) and a sediment sample (CB-41) collected from a settling tank associated with an oil-water separator located on the Basin Oil property (see Section 2.4.1). Analytical results from this sampling program were compiled in 2008 and reviewed by the City in 2008 (Integral 2008b). The dioxin/furan TEQ for the street dust sample (SD52) and settling tank sample (CB-41) both exceeded the SL (11 ng/kg; [MTCA Method B/TSCA]), atwas 90.5 ng/kg and 15.2 ng/kg, respectively., exceeding the SL (11 ng/kg). The street dust at this sampling location and the immediate vicinity was removed in 2005 based on PCBs as part of the City's independent cleanup action (Section 2.2.4). In 2008, the City, in coordination withas directed by EPA, conducted a follow-up sampling program to assess whether there were any other locations with elevated dioxin concentrations in the vicinity of the 90.5 ng/kg result. Sixteen Fifteen samples were collected from the Adjacent Streets in 2008 (Map 2-3735) and analyzed for dioxins and furans and PCBs. Nine locations had dioxin/furan TEQs that were greater than the SL. The highest dioxin/furan TEQ was detected in borehole P94 (84 ng/kg in the 0.1--to--1.0-ft interval) on Dallas Avenue S immediately east of the intersection with 16th Avenue S (south of the Marina). The next highest dioxin/furan TEQ was detected on S Donovan Street adjacent to Basin Oil and the T-117 Upland Study Area (30 ng/kg in the 0.4-to-1.0-ft depth interval at P100), Dallas Avenue S immediately west of 17th Avenue S (32.4 ng/kg in the 0.1-to-1.0-ft depth interval at P95), and Dallas Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 68 Avenue S at the intersection with 16th Avenue S (21.4 ng/kg in the 0.4-to-1.0-ft depth interval at P90). Nine Eight MIS split samples collected in 2009 were analyzed for dioxins and furans by Ecology. MIS samples were collected from the surface (0.0-to-0.2-ft [0.0-to-2.0-in.] depth interval 0.0-to-0.2-ft depth interval) and subsurface (0.2-to-0.5-ft [2.0-to-6.0-in.] depth interval 0.2-to-0.5-ft depth interval) at DU16 and DU17, located on the west and east sides of 16th Avenue S, respectively (Map 2-3735). Dioxin/furan TEQs ranged from 9.58 ng/kg in the at DU16-0.0-to-0.2-ft (0.0-to-2.0-in.) depth interval of DU16 to 43.8 ng/kg in the 0.0-to-0.2-ft (0.0-to-2.0-in.) depth interval at DU17-0.0-0.2. Surface and subsurface samples were collected at DU18 and DU19, located along the west and east portions of the bank, respectively, along lower S Donovan Street (Map 2-3735). Dioxin/furan TEQs ranged from 30.4 ng/kg to 51 ng/kg at DU18 (0.0-- to-- 0.5-ft and 0.2- to- 0.5 5-ft bgsdepth intervals, respectively). Dioxin/furan TEQs in all samples exceeded 11 ng/kg,the SL with the exception of one sample at DU16 (9.58 ng/kg at the DU16-0.0-0.20.0-to-0.2-ft depth interval). Map 2-33 386 shows the dioxin/furan TEQ soil sample locations that were in areas where soil was removed as part of the City's 2004 and 2005 clean-up actions or were superseded by subsequent sampling in 2009.presents the dioxin/furan TEQs in soil that were removed from or superseded by MIS results. 2.3.3.2 Residential Yards This section summarizes the data obtained from soil investigations conducted within the Residential Yards between 2004 and 2009. Several investigations were conducted within the Residential Yards to support the City's site characterization and independent cleanup actions between 2004 and 2006 (Integral 2006b) and to support boundary refinement activities completed since the Adjacent Streets were included in the T-117 EAA in 2007 (Integral 2009; Windward and Integral 2009). The detection of PCBs in Residential Yards samples collected in 2008 led to a request by In the case of residential yards, DUsto encompass individual residential properties or portions thereof based on a conceptual model of land use for residential properties (i.e., differences in uses for front yards and backyards) and proximity to potential PCB track-out in streets. The MIS increments were aggregated to form a single composite to provide an average chemical concentration for soil in that DU (Integral 2009). Some of the 2009 sampling completed in the Adjacent Streets was also completed using MIS. EPA has determined that results from previous investigations that were based on point samples located within the 2009 DU areas were to be superseded by results of the 2009 MIS sampling in that location. Appendix C includes a complete list of available data for each chemical analyzed in the Residential Yards. Appendix C also identifies samples that were removed during the City's independent cleanup actions or data that were superseded by subsequent Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 69 MIS composite sampling data; these data are presented to illustrate the current spatial distribution of contaminants. PCBs A total of 175 point and MIS 206 soil samples collected from within the Residential Yards have been analyzed for PCBs. The source soils from for which 4544 of these 175 samples were collected have since beenwas removed in conjunction with the City's independent 2004 and 2005 cleanup actions., and PCB concentrations data for 47 of the 175 samples were superseded by the 2009 MIS sampling (as presented on Map 2-31). PCB concentrations associated with Residential Yards soil are presented on Map 2-- 38367. Sampling performed during the City's cleanup near the intersection of Dallas Avenue S and 17th Avenue S (across from the entrance to the T-117 Upland Study Area) indicated that total PCB concentrations greater than the SL extended to depths that were similar to those in the Adjacent Streets. All PCB-contaminated soil detected within the residential lots was excavated and disposed of at an offsite landfill (Hart Crowser 2005). Thirty-four Residential Yards point samples were collected in 2008 to assess the concentrations of PCBs in residential soils near the ROWs. Twenty--eight four of these point sampling results were superseded by 2009 MIS results collected from the same yards. In locations where 2008 sampling results were not superseded by 2009 MIS results did not supersede the 2008 results for Residential Yards (YC samples) or discrete yard parking strip samples (YS samples) (sampling locations YC17 and YC18, which were east of 16th Avenue S), total PCB concentrations ranged from 0.12 to 0.26 mg/kg (Windward and Integral 2009). MIS sampling conducted in 2009 was designed to identify average total PCB concentrations in soil within individual DUs. The DUs were delineated collaboratively with EPA to encompass individual residential properties or portions thereof based on a conceptual site modelCSM of land use for residential properties (i.e., differences in uses for front yards and backyards) and proximity to potential PCB track-out in Adjacent Streets (Integral 2009). Fifty Residential Yards MIS samples were collected in 2009.Total PCB concentrations ranged from 0.043 mg/kg to 2.1 mg/kg at DU32 (0.0 -to to-0.2 -ft depth intervalbgs). MIS DUs results with PCB concentrations that exceeded 1 mg/kg included DU01, DU14, DU32, and DU35. Map 2-38 367 provides presents the PCB resultsconcentrations (with replicates averaged) the PCB results for the Residential Yards DUs. Note that for the purposes of removal boundary delineation, total PCB concentrations for each DU were adjusted for variance at the direction of EPA (Appendix KL) as discussed in Section 4.4.3. Map 2-33 31 presents the total PCB concentrations in soil that were removed from or superseded by MIS results. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 70 Dioxins and Furans Dioxin/furan TEQs in soil samples collected from the Residential Yards are shown on Map 2-39 3738 and presented in Appendix C. Nineteen composite samples (0.0-to-0.5- ft depth interval) and four three discrete point samples were analyzed in 2008 to evaluate the extent of contamination in Residential Yards (Windward and Integral 2009) and had concentrations up to 395 ng/kg (the 395 ng/kg result was considered to be an outlier because of carbon fragments in the sample matrix; the next highest concentration was 50.1 ng/kg). Fourteen Thirteen of these samples, including the sample with the concentration of 395 ng/kg, were subsequently superseded by 2009 MIS samples. Map 2-36 shows the dioxin/furan TEQ soil samplinge locations that were in areas where soil was removed as part of the City's 2004 and 2005 cleanup actions or were superseded by subsequent sampling conducted by the City in 2008 and 2009.Samples collected in Residential Yards that had soil removed or samples that were superseded by subsequent sampling are shown on Map 2-33. Dioxin/furan TEQs of in non-superseded Rresidential Yyard composite samples (shown on Map 2-378) ranged from 4.69 ng/kg at YC16abc to 16.0 ng/kg at YC12abc. Samples from YC12abc, YC13abc, YC14abc, and YC19abc were the only Rresidential Yyard composite non-superseded samples that exceeded the SL (11 ng/kg; [MTCA Method B]). Twenty-four MIS sample splits were provided to Ecology for dioxin and furan analysis. The highest dioxin/furan TEQs were detected in DU01 at the west end of Dallas Avenue S (50.1 ng/kg from the 0.0- to- 0.2- ft in [0.0-to-2.0-in.] depth interval and 38.2 ng/kg from the 0.2 2-to to-0.5 5-ft [2.0-to-6.0-in] in depth interval);) ( (Map 2-- 3938). All MIS samples but one sample (in the 0.0-to-0.2-ft depth interval from DU03- 0.0-0.2) exceeded the SL (Ecology 2009a). 2.3.4 Groundwater Groundwater data have been collected from both monitoring wells and intertidal seeps throughout the T-117 EAA and vicinity since 1991. Historical (pre-2003) groundwater conditions are detailed in the data gaps report (Windward et al. 2003). Groundwater samples analyzed during sampling events conducted between 2003 and 2009 are considered most representative of current conditions and are summarized in Section 2.3.4.1this Section. Section 2.3.4.1 discusses groundwater results for the T-117 Upland Study Area, and Section 2.3.4.2 discusses the groundwater results for Adjacent Streets and Residential Yards Study Area. Section 2.3.4.3 discusses the seep water results. The T-117 EAA monitoring well network currently consists of 13 wells. Seven wells (MW-02, MW-03, MW-04R, MW-05R, MW-06, MW-07, and MW-08R) are located on the T-117 Upland Study Area, four wells (MW-01, MW-09, MW-10, and MW-11) are located just upgradient of the T-117 Upland Study Area on Dallas Avenue S, and two wells (MW-12 and MW-13) are upgradient of Basin Oil on 17 th Avenue S and Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 71 S Donovan Street. Locations of groundwater monitoring wells are shown on Maps 2-7 and 2-8. Several seeps discharge from the shoreline bank. Many of these seeps are seasonal, and the locations and flow rates of these seeps can vary. One seep is relatively large with a consistent location and flow rate; the locations of sampled seeps are shown on Map 2-7. Appendix C includes all groundwater sampling data from 1991 through 2009 and presented in Appendix C. Appendix B presents the assessment and development of groundwater screening and site-specific removal action levels based on the groundwater monitoring results, groundwater quality criteria to be achieved at the point of discharge, and a detailed evaluation of the potential for contamination from former asphalt plant operations to have impacted groundwater beneath the Adjacent Streets and Residential Yards Study Area. 2.3.4.1 T-117 Upland Study Area Groundwater Data Groundwater monitoring was occasionally conducted in the T-117 Upland Study Area between 2003 to 2005. Below is a summary of the data results from the seven consecutive quarters of groundwater monitoring conducted since first quarter 2008. The following discussion is limited to the first quarter 2008 through the third quarter 2009 groundwater monitoring events because the fourth quarter 2009 groundwater monitoring event had not been completed at the time that the EE/CA COC analysis was conducted. Appendix C includes summary tables that contain all available data, including data from the fourth quarter 2009 event. PCBs Total PCBs were detected in 23 of 70 samples. Twenty-one of twenty-threeAll total PCB detections were above the SLs (0.000064 g/L) for total PCBs. The maximum highest total PCB concentration was 2.0 g/L (at MW-03). PCBs were detected in six of seven T-117 Upland Study Area wells during one or more sampling events. Aroclor 1260 was detected in all detected samples, and Aroclor 1254 was detected in two samples (MW--05R and MW-08R). TPH Total TPH was detected in 17 of 57 samples and exceeded the SL (0.5 mg/L) in 16 samples. The maximum detected total TPH concentration was 22 mg/L (at MW-03). Total TPH exceeded the SL for in one or more samples in from two T-117 Upland Study Area wells (MW-02 and MW-03).of five T-117 Upland Study Area wells. cPAH cPAHs were detected in 4 of 54 samples from three of seven T-117 Upland Study Area wells (MW-03, MW-02, and MW-05R). One sample exceeded the SL (0.018 g/L) for cPAH TEQ. The maximum cPAH TEQ was 0.20 g/L (at MW-05R). Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 72 Total cPAH TEQ were detected in 4 of 54 samples. One sample exceeded the SL for total cPAH TEQ. The maximum total cPAH TEQ was 0.20 g/L (MW-05R). Total cPAH TEQ was detected in three of seven T-117 Upland Study Area wells. Other SVOCs and VOCs The only SVOC detected above SLs in groundwater collected from T-117 Upland Study Area wells was BEHP. BEHP was detected in 15 of 52 samples and exceeded the SL (2.2 g/L) in 4 samples from three wells (MW-04R, MW-05R, and MW-06). The maximum BEHP concentration was 16 J g/L (at MW-04R). Phenol has been detected but no concentrations have been above the SL (1,700,000 g/L). Phenanthrene has also been detected; however, no applicable SL based on the protection of a surface water receptor is available. BEHP was detected in 15 of 52 samples and exceeded the SL in 4 samples. The maximum BEHP concentration was 16 J g/L (MW-04R). BEHP exceeded the SL for one or more samples in three of six T-117 Upland Study Area wells. No other SVOCs or VOCs exceeded SLs for any samples. Metals Seven metals (arsenic, copper, cadmium, chromium, lead, silver, and zinc) have been detected in groundwater. Only Arsenic, copper, and silver have been detected in groundwater above the SLs. Arsenic was detected in all T-117 Upland Study Area wells and exceeded the SL (0.00014 mg/L) in 16 of 48 samples from all seven wells. Copper was detected in 12 of 43 samples and exceeded the SL (of 0.0031 mg/L) in six detected samples from four T-117 Upland Study Area wells (MW-03, MW-04, MW-06, and MW-08R). Silver was detected in 7 of 43 samples and exceeded the SL (of 0.0019 mg/L) in all detected samples from four T-117 Upland Study Area wells (MW-04, MW-05R, MW-06, and MW-08R). The silver reporting limits for all non-detect samples also exceeded the SL. Dioxins and Furans Groundwater samples collected during the fourth quarter 2008 sampling event were analyzed for dioxins and furans. Groundwater samples were collected from three wells (MW-05R, MW-08R, and MW-10). All groundwater sample dioxin and furan concentrations were below detection limits, with the exception of one congener from MW-08R (1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin), which resulted in a dioxin/furan TEQ of 3.0-9 g/L), exceeding the dioxin/furan TEQ SL of 5.0-9 g/L. No samples exceeded the groundwater SLs for dioxins and furans. Light Non-Aqueous-Phase Liquid (LNAPL) During the 2004, 2005, and 2008 groundwater monitoring events, tidal studies were conducted with an oil-water interface probe to determine the presence or absence of light non-aqueous-phase liquid (LNAPL) in the groundwater monitoring wells. In 2004 and 2008, no LNAPL was detected in any of the wells (Windward et al. 2005d; Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 73 ENSR|AECOM 2008). In 2005, trace amounts of LNAPL (essentially a sheen [i.e., < 0.01-ft thick]), were detected in two wells (MW-02 and MW-07) (Windward et al. 2005d). During the 2009 second quarterly groundwater sampling event, a trace to heavy trace sheen (with no measurable product thickness) was observed on the groundwater at MW-03 (AECOM 2009b). 2.3.4.2 Adjacent Streets and Residential Yards gGroundwater dData Groundwater sampling has not been conducted beneath the Adjacent Streets and Residential Yards Study Area based on the findings of the 2005 site characterization work plan (Integral 2005) and other investigations. The work plan noted that the depth of contaminants in soil was shallow (maximum depth of 8 ft) relative to the depth of groundwater (approximately 12 ft below Dallas Avenue S), the solubility and consequent immobility of PCBs in soils was low, and that PCBs were detected only infrequently and at low concentrations in groundwater from T-117 Upland Study Area wells where PCB-impacted soil was in contact with groundwater. Although groundwater investigations have not been conducted in the Adjacent Streets Study Area, several monitoring wells have been installed in and around the Adjacent Streets, including the wells MW-01 MW-09, MW-10, MW-11, MW-12, and MW-13 and three wells installed at the Marina. The results of groundwater monitoring associated with these wells and soil conditions in the Adjacent Streets Study Area are evaluated in Appendix B. This evaluation shows that while some chemicals have been sporadically detected in groundwater below or immediately downgradient of Basin Oil, the presence of a groundwater contamination beneath the Adjacent Streets Study Area resulting from former asphalt plant operations is unlikely. Groundwater samples collected from five locations in and around Basin Oil and from three wells at the Marina indicated that PCBs were limited to a single detection (at MW-01), which was not confirmed with subsequent monitoring The solubility of PCBs, dioxins and furans, PAHs, TPH-D, and TPH-O is low, and the data indicate that where these chemicals were detected in surface and subsurface soils, they have not leached to groundwater in the 30-plus years that they have been present. The potential for contaminant leaching in the future will be further reduced by removal of soils with residual contamination as part of the permanent remedy for the site. 2.3.4.3 Seeps Three seeps (Map 2-7) were identified and sampled in 2003 (Windward et al. 2005d). The seep water samples were analyzed for PCBs, SVOCs, PAHs, other SVOCs, and total metals. As presented in Appendix C, the only consistently detected chemicals were BEHP, copper, chromium, and zinc. PCBs were detected in one seep sample (SW3); however, it is possible that the PCBs were associated with contaminated fine particles present in the seep sample instead of the water. This seep was subsequently re-sampled, and the sample was centrifuged prior to analysis to remove any fine particles, resulting in a non-detection for PCBs. It is unknown whether the PCBs were Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 74 attached to fine particles traveling with the seep water or if contaminated particles became entrained in the sample during collection. T-117 seep sample specific conductivity measurements were compared with T-117 the groundwater and LDW surface water specific conductivity measurements to assess whether the T-117 seeps were representative of bank- stored infiltrated LDW surface water or T-117 groundwater. The fField parameters resultsmeasurements forT-117 seep and groundwater well samples are summarized in Tables 2-3 and 2-4. The average specific conductivity for the LDW in this reach of the river iwas 30,300 S/cm based on shallow measurements at the South Park Bridge in 2005 (Mickelson and Williston 2006); these shallow measurements are more representative of water that would infiltrate at T-117 and are less saline than deeper water, which would be more influenced by salt water. The specific conductivity of the seep samples varied from 5,200 to 18,500 S/cm, with an average of 12,200 S/cm. Eight of the thirteen monitoring wells had average specific conductivities less than 1,000 S/cm. The highest specific conductivities for monitoring wells were at MW-4R, MW-5R, MW-6, and MW-8R; these four shoreline wells hadve average specific conductivities of 16,300, 6,600, 3,400, and 14,900 S/cm, respectively. The other well with elevated specific conductivity was MW-13, located upgradient and near the bedrock outcropping describe in Section 2.1.5.2, with an average specific conductivity of 1,500 S/cm. Based on these data, it appears that the groundwater samples may have been diluted by LDW surface water more than is typically anticipated. Table 2-3. Summary of seep sampling field parameters at T-117 Early Action Area Specific Dissolved Date Temperature Conductivity Oxygen ORP Turbidity Seep Sampled (C) (S/cm) (mg/L) pH (mV) (NTU) Seep 1 12/23/2003 7.46 5,213 9.22 7.14 467 nc Seep 2 12/23/2003 7.84 14,803 8.38 6.69 467 nc 12/23/2003 9.28 18,527 7.81 7.09 358 nc Seep 3 4/8/2004 9.6 14,781 9.72 9.11 79 1.12 Seep minimum 7.46 5,213 7.81 6.69 79 1.12 Seep maximum 9.6 18,527 9.72 9.11 467 1.12 Seep mean 8.25 12,223 8.79 7.31 384 1.12 Note: Stabilized field parameters are the values measured just prior to the collection of seep samples. C centigrade nc not collected NTU nephelometric turbidity unit ORP oxidation-reduction potential Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 75 Table 2-4. Summary of monitoring well parameters at T-117 Early Action Area Temperature Specific Conductivity Dissolved Oxygen ORP Turbidity (C) (S/cm) (mg/L) pH (mV) (NTU) Well ID Min Max Mean Min Max Mean Min Max Mean Min Max Mean Min Max Mean Min Max Mean MW-1 11.67 15.20 13.11 550 907 668 5.94 6.21 6.08 0.20 1.55 0.79 37.3 79.0 53.8 -4.4 1.8 0.0 MW-2 10.46 19.42 14.55 533 1,136 691 6.45 7.61 6.79 0.24 1.34 0.54 -132.5 48.3 -74.0 0.0 8.3 2.3 MW-3 10.41 16.86 13.72 418 502 471 6.27 6.47 6.35 0.14 1.43 0.85 -60.2 10.7 -30.9 0.0 8.9 4.0 MW-4R 8.37 16.03 11.88 8,885 25,829 16,297 6.79 8.33 7.28 2.73 8.40 5.67 -165.2 272.4 87.0 0.0 9.5 2.9 MW-5R 9.49 18.68 12.58 1,237 17,594 6,585 6.76 8.31 7.24 3.54 9.98 7.14 -64.1 192.5 103.3 0.0 2.7 0.9 MW-6 10.89 15.41 13.49 1,145 4,590 3,368 6.53 6.96 6.78 3.35 6.32 4.94 21.8 204.9 126.1 5.2 7.8 6.6 MW-7 11.99 16.76 13.95 122 268 190 5.80 6.24 6.00 2.45 6.82 4.93 24.4 164.4 124.0 0.0 7.0 2.7 MW-8R 8.76 15.86 11.91 4,214 29,248 14,896 6.73 8.84 7.72 3.64 9.06 6.27 -34.4 233.3 102.6 0.2 1.3 0.7 MW-9 12.34 13.21 12.78 307 556 432 5.95 6.11 6.03 4.75 5.67 5.21 180.1 232.4 206.3 0.65 1.04 0.85 MW-10 10.17 12.96 11.64 214 422 328 5.48 5.95 5.71 0.65 1.84 1.38 66.7 181.3 144.7 1.5 14.0 5.1 MW-11 10.44 17.61 13.64 340 825 624 5.90 7.06 6.40 0.18 0.74 0.44 -238.4 187.7 32.8 0.0 5.0 1.3 MW-12 14.51 19.70 17.06 436 868 604 7.83 8.33 8.16 0.39 3.35 1.43 10.10 105.70 69.03 0.56 90.60 31.92 MW-13 16.27 22.81 19.80 1,222 2,138 1,532 7.16 7.64 7.45 0.12 4.01 1.59 -91.40 73.30 -35.37 0.29 18.00 6.37 Note: Stabilized field parameters are the values measured just prior to the collection of groundwater samples. C centigrade ID identification NTU nephelometric turbidity unit ORP oxidation-reduction potential Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 76 2.4 RECONTAMINATION ASSESSMENT AREAS This section describes the RAAs (Basin Oil and the Marina) and summarizes available data relative to the SLs developed in Section 3 for all media for soil and sediment and Appendix B for groundwater. The complete dataset for the RAAs is presented in Appendix CF. The contaminants identified in at these RAAs at concentrations above SLs will be incorporated into the analysis of potential recontamination of the T-117 Sediment Study Area from these two areas presented in Section 5.2. 2.4.1 Basin Oil parcels 2.4.1.1 Site dDescription and hHistory Basin Oil's primary operations occurred in the triangular-shaped property (8661 Dallas Avenue S) bounded by Dallas Avenue S to the east, Donovan Street S to the south, and 17th Avenue S to the west (Map 1-1). Basin Oil operated at the site between 1987 and 2004 (Ecology 2005a). Prior to that time, the site served as the location of a private residence. Three additional business entities are documented as having operated on the property at one time or another during the Basin Oil tenure: Frontwater, Inc.; Basin Tank and Environmental Services, Inc.; and Northwest Antifreeze Service, Inc. Basin Oil also leased property on the T-117 Upland Study Area, near the former asphalt plant facility located across the street to the east, where they stored materials in drums and in a tank. Basin Oil also stored drums and trucks at 8617 17th Avenue S, a residential property, located across the street to the west. Basin Oil was a collector, transporter, and marketer of used oil. According to Basin Oil's spill prevention, control, and countermeasure plan (Basin Oil 1995), materials handled routinely at the facility included lubricating oil, Bunker C heating oil, diesel fuel, crude oil, jet fuel, and gasoline. Used oils are generally known to contain PAHs. Recycled and waste oils have been known to occasionally contain low concentrations of PCBs and chlorinated solvents. Based on Ecology inspection reports (Ecology 2000; Hohmann 1992), Frontwater and Basin Tank and Environmental Services handled similar materials. Northwest Antifreeze Service handled new and used antifreeze. Used antifreeze can contain metals such as lead and cadmium. According to a site assessment conducted in 1996 (Creative Environmental Technologies 1996), the property was first developed and used for residential purposes in the 1930s and was converted to an oil recycling facility in the late 1980s. At the time of the 1996 site assessment, the northern portion of the property was paved, and the southern portion was not. Standing water and tanks without containment were both observed on the southern portion (Creative Environmental Technologies 1996). Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 77 Basin Oil was visited by regulators on at least 12 occasions between December 1992 and December 2004 in the course of site inspections or in response to incident reports or neighborhood complaints. Concerns and incidents included, but were not limited to, the items listed below (Ecology 1992a, b, 1993a, 1994b, a, 2003; Hohmann 1992). Improper designation and labeling of wastes, including the potential handling of hazardous wastes Errors, omissions, and discrepancies in waste manifests, including an allegation of forgery Inappropriate waste storage containers Insufficient secondary containment A spill of 500 to 600 gal. of used fuel oil that occurred during Basin Oil operations on the asphalt plant property in October 1993 Inadequacies in the spill prevention, control, and countermeasure plan; the stormwater pollution prevent plan; and in emergency planning procedures A more detailed discussion of selected compliance inspections and site visits is available in the T-117 summary of existing information and data gaps analysis report (Windward et al. 2003). Prior to 2005, surface runoff from Basin Oil and the Adjacent Streets flowed onto the T-117 Upland Study Area and into the catch basins at the south side of the T-117 Upland Study Area (SAIC 2007a). As described in Section 2.1.3.3, stormwater exiting the site is now captured within the temporary stormwater collection system installed during the City's independent cleanup action in the Adjacent Streets. Between 2004 and early 2008, the Basin Oil property facility underwent demolition and stabilization, including the excavation of contaminated surface soil and backfilling. Soil excavation occurred to depths of 2 to 2.5 ft across the site, with excavations as deep as 4 ft in areas with visual or olfactory evidence of petroleum (Ecology 2005a; Thomas 2008b). Site investigation samples were collected by Ecology in 2009; these results are further discussed and summarized below. Excavation to a depth of about 6 in. was performed in the drum storage area on the residential property at 8617 17th Avenue S (Thomas 2008a). That property has been sold to the owner of the Marina and currently is being used for boat storage. An application form for Ecology's Voluntary Cleanup Program (ENSR 2006) indicates that Basin Oil is intended to be used for boat storage. 2.4.1.2 Summary of existing environmental data Available data for Basin Oil includes historical (e.g., pre 2008 soil removal) soil, groundwater, and liquids and sludges from tanks and drums at Basin Oil and post post-2008 soil and groundwater data. The historical samples are not necessarily representative of current site conditions inasmuch as some or all of the soil sampled Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 78 may have been removed during the Basin Oil cleanup; however, they are discussed below because they may have been potential previous source contamination to the T-117 EAA. The most recent data are from analyses performed on investigational samples collected in 2008 and 2009 from Basin Oil following soil removal by the site owner, and one sample (Drexler 2007) collected in 2007 from the 8617 17th Avenue S. The recent samples are considered to be representative of current conditions and are summarized below. Both historical and recent sampling locations are shown on Map 2-3940 and results are presented in Appendix C and summarized in Appendix F. The historical and recent data are further evaluated in the recontamination assessment presented in Section 5. Soil Historical Results The historical soil dataset for Basin Oil is limited and consists of 8 samples. One surface soil sample and two subsurface samples were collected on the Basin Oil property outside the fence line in the MW-01 boring in July 1991 (Parametrix 1991). Two surface soil samples were collected and composited during the 1996 site assessment (Creative Environmental Technologies 1996). Two samples were collected from onsite drainage structures, a settling tank associated with an oil/water separator and an area drain (CB41 and CB42, respectively), during a joint City/Ecology site visit in July 2004 (Ecology 2005a). EPA collected a surface soil sample during a site visit in May 2007 (Rodin 2007). Detected chemicals in soil collected from Basin Oil are presented in Appendix F. Historical Basin Oil soil data were screened using the SLs developed for the T-117 EAA (Section 3). One of the 1996 composite surface samples and samples from two subsurface intervals from the 1996 MW-01 boring exceeded the PCB SL (0.5 mg/kg). TPH exceeded its SL in CB-41 and CB42. The dioxin/furan TEQ in CB-41 also exceeded the SL. Chromium was the only metal detected in soil above the SL (which was detected in one sample from an MW-01 subsurface sample interval). A storm solids sample obtained from CB41 exceeded the SL for lead. Current Results In May 2009, Ecology collected surface and subsurface soil from 10 locations on the Basin Oil property (Map 2-3940) (Ecology 2009b). In May 2007, Basin Oil reported concentrations for a soil sample collected at the 8617 17th Avenue S property (Ecology 2008). Basin Oil soil data were screened using the SLs developed for the T-117 EAA (Section 3). Surface soil concentrations Concentrations of arsenic, TPH (lube oil and gas), cPAHs, total PCBs, ethylbenzene, and xylenes in surface soils were greater than their respective SLs. The total PCB concentration in one 12.5-ft-deep soil sample Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 79 (BSB-3) was greater than the SL. The results of the recent soil sampling at the Basin Oil property are presented in Appendix C and summarized in Appendix F. Groundwater Prior to 2009, only one groundwater monitoring well, MW-01, existed at Basin Oil, located on the southeast property boundary (Map 2-79). MW-01 has been sampled eight times between 1991 and 2008 (Windward et al. 2003; ENSR|AECOM 2008). Groundwater data from MW-01 collected during sampling events between 2003 and 2009 are considered to be the most representative of current conditions and were included as part of the groundwater summary presented for the T-117 EAA in Section 2.3.4.1. Tanks and Drums EPA collected samples of liquid and/or sludge from two tanks and four drums during a site visit in May 2007 (Rodin 2007). The tank and drum data do not directly represent site environmental conditions but because they are indicative of past operations on the site, they provide an indication of chemicals that could be present in the site soil and groundwater. Aroclor 1260 was detected in sludge from one drum but not in sludge or liquids from the other three drums or the two tanks. Petroleum was not analyzed in the tank or drum samples. Chrysene, seven non-carcinogenic PAHs, three phthalates, BTEX, one chlorinated solvent, and two non-chlorinated solvents were detected in tank or drum samples. Arsenic, chromium, copper, lead, nickel, zinc and 16 other metals were detected in tank and drum samples. The concentrations of chemical analyses of the tank and drum samples are presented in Appendix C and summarized in Appendix F. 2.4.2 South Park Marina 2.4.2.1 Site dDescription and hHistory The Marina is located at 8604 Dallas Avenue S and is adjacent to the T-117 Upland Study Area to the north. Since the early 1970s, the site has been used as a small boat marina and repair and maintenance facility. Activities at marinas elsewhere are known to result in copper, lead, TBT, PAH, and phthalate impacts. Best management practices (BMPs) are in place and Ecology has inspected the site. The Marina BMPs include the use of vacuum sanders, tarps to catch debris, routine sweeping of boat maintenance areas, and a closed-loop wash system. Ecology concluded that the potential for sediment recontamination associated with current operations is believed to be low (SAIC 2007b). In the early to mid-1950s, A&B Barrel reconditioned and repainted drums on the southeastern portion of the Marina using sodium hydroxide as a cleaning agent. Liquid waste was discharged to an onsite pond that discharged to the LDW. The northern half of the Marina was also formerly a mobile home park. Other former Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 80 operations at the Marina site included the North Star Trading Company, Evergreen Boat Transport, R.P. Boatbuilding, and Dekker Engineering. 2.4.2.2 Summary of existing environmental data All available data collected from the Marina is are relatively recent and representative of current conditions. The results of the Marina samples are further evaluated in Section 5. All of the results from the Marina investigation are presented in Appendix C and summarized in F. Soil and Sediment In 2004 and 2006, the Port collected and analyzed seven soil samples for PCBs (including a duplicate sample) near the boundary between the Marina and T-117 Upland Study Area. These sampling locations are shown on Map 2-4140, and the PCB concentrations are presented in Appendix F. PCBs were detected at relatively low concentrations in samples from all locations. At two locations (T-117 A11 and T-117 A12), Aroclor 1254 was detected in addition to Aroclor 1260 (Aroclor 1260 is the predominant Aroclor at the T-117 EAA). TPH was also analyzed and detected in one sample and the field duplicate sample from location T-117-A10, but at concentrations well below the MTCA criteria (2,000 mg/kg). Ecology recently conducted a reconnaissance-level environmental investigation of the area formerly occupied by A&B Barrel that included subsurface soil sampling throughout the area formerly occupied by A&B Barrel and soil and sediment sampling along two transects perpendicular to the shore (SAIC 2008). Thirteen subsurface soil sampling locations were collected and analyzed for PCBs, pesticides, SVOCs, VOCs and metals. Metals, PCBs, pesticides, PAHs, TPH and VOCs in soil samples collected from the Marina were detected above their respective SLs (SAIC 2009). Three samples were collected along transects near the T-117 Upland Study Area and Marina boundary and in front of the former A&B Barrel pond location (Map 2-394140). Two soil samples were collected along each transect (one from the top of the bank and one from just above the high water mark) and one sediment sample (collected from the toe of the riprap bank). These samples were collected primarily to determine if there were any impacts from the Marina bank soil to the sediment below. PCB concentrations in two sediment samples (identified as Sediment Transect A and Sediment Transect-B on Map 2-810) exceeded the SL for total PCBs (as Aroclor 1260), indicating that PCBs from the Marina bank may have the potential to recontaminate the sediment below. However, the total PCB concentrations in the soil samples from Transects A and B (upgradient of the sediment samples) ranged from 0.073 to 0.17 mg/kg dry weight (dw) (0.61 to 8.5 mg/kg OC6). Groundwater Ecology's investigation of the area formerly occupied by A&B Barrel also included two rounds of groundwater monitoring at three shoreline wells. Groundwater samples Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 81 collected in October 2007 and March 2008 contained pesticides (detected in MW-3) and arsenic (detected in all three site wells) above the Ecology screening criteria (SAIC 2009). One of the monitoring wells was located downgradient of a pond that reportedly was used for liquid waste disposal in the 1950s. The other two wells were installed in locations selected to characterize groundwater in other areas with a high potential for impacts. Recent tidal data collected from T-117 EAA wells suggest that groundwater flow is parallel to the Marina/T-117 Upland Study Area property line. Based on this groundwater flow pattern, migration from the Marina to the T-117 Upland Study Area is unlikely. Map 2-4140 provides the locations of the monitoring wells and Map 2-57 presents the groundwater flow pattern. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 82 3 Streamlined Risk Assessment This section presents the streamlined risk assessment. As described in the EE/CA guidance (EPA 1993), a streamlined risk assessment is an important component of an NTCRA. This assessment is intermediate in scope between the limited risk assessment conducted for emergency removal actions and the conventional baseline assessment normally conducted for remedial actions. The streamlined risk assessment is presented in this section, which includes: The identification of exposure pathways to potential receptors through the development of a CSM (Figure 3-1) A comparison of SLs to site-specific data to determine media- and subarea-specific COPCs for these pathways The identification of COCs for which site-specific removal action levels (i.e., RvALs) are have been derived etermined in (see Section 4.3) The purpose of this streamlined risk assessment is to support the development of the NTCRA removal area boundary and design (i.e., alternative selection) and establish the framework for post-NTCRA monitoring. The streamlined risk assessment ultimately must demonstrate that the NTCRA is protective of ecological and human receptors. This assessment is designed to be consistent with both MTCA and CERCLA risk evaluation frameworks to ensure that all areas within the T-117 EAA that pose an unacceptable risk will be addressed by the NTCRA. As specified in the EE/CA guidance (EPA 1993), the streamlined risk assessment focuses on T-117 EAA media that are the focus of the NTCRA, including sediment in the T-117 Sediment Study Area and soils in the T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area. Groundwater considerations (i.e., groundwater potability, groundwater COCs, and RvALs) are discussed in Appendix B, and an assessment of the potential for sediment recontamination from groundwater has been incorporated into the development of groundwater RvALs presented in Section 4.X3. 3.1 CONCEPTUAL SITE MODEL AND PATHWAY IDENTIFICATION A CSM for the T-117 EAA was developed to present the relationships among confirmed and potential sources, release mechanisms, transport mechanisms, exposure media, exposure routes, and potential receptors (Figure 3-1). A comprehensive CSM is an essential part of the streamlined risk assessment because it identifies pathways that must be considered in the design and successful implementation of an early action. The CSM focuses primarily on current release and transport mechanisms by which ecological and human receptors could be exposed. A Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 83 summary of historical contaminant sources and associated site data was presented in Section 2. As discussed in Section 1, the T-117 EAA includes the T-117 Sediment Study Area, the T-117 Upland Study Area, and the Adjacent Streets and Residential Yards Study Area (Map 1-1). The CSM includes all the study areas, although the importance of specific transport mechanisms and exposure media varies significantly by study area, as described below. 3.1.1 Primary sources As shown in Figure 3-1, both historical and current primary sources have been identified in the T-117 EAA. The principal historical source of contaminants was the former asphalt manufacturing facility, which was located on property that is now part of the T-117 Upland Study Area. The facility has been removed and is no longer a source of contamination, although legacy contamination from the facility may still be transported within and potentially outside of the T-117 EAA via secondary transport mechanisms. Other nearby potential primary sources of contaminants (both historical and current) include the Basin Oil property and the Marina, both of which have been identified in this EE/CA as RAAs (Map 1-1). These properties are discussed in more detail in Sections 2.4 and 5.2. Other regional sources that may have contributed to T-117 EAA contamination, and may continue to do so, may also exist within the surrounding urban area. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 84 Figure 3-1. T-117 conceptual site model for current site conditions Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 85 3.1.2 Primary release and transport mechanisms Contaminant release mechanisms refer to the manner in which contaminants are released from the primary source. Primary release mechanisms associated with the former asphalt manufacturing facility included upland process-related releases, spills, and the combustion of fuel oils, including recycled waste oils and PCB-contaminated oil. The current and historical combustion of fuel and heating oils at other properties in the vicinity of the T-117 EAA also represents a primary release mechanism. Urban and industrial sources outside the T-117 EAA could also have resulted in releases to sediment, soil, groundwater, stormwater, or air within the T-117 EAA. Contaminant transport mechanisms refer to the physical processes that move contaminants from one area to another, including within the T-117 EAA and from outside areas to the T-117 EAA. In the T-117 CSM (Figure 3-1), a primary transport mechanism refers to a process that moves contaminants from the primary source to one or more study areas within the EAA. The primary transport mechanism from combustion sources is atmospheric deposition, either as dry deposition (during dry weather) or as wet deposition (during rain events). This transport mechanism likely deposited contamination from the former asphalt manufacturing facility and potentially other offsite sources to sediments in the T-117 Sediment Study Area and soils in the T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area. Other primary transport mechanisms that likely moved contamination from the former asphalt manufacturing facility to areas within the T-117 EAA include track-out, filling and dumping, dust generation and transport, surface water flow (as stormwater), and groundwater migration, infiltration, and adsorption/desorption (Figure 3-1). Each of these primary transport mechanisms is briefly described below. Track-out refers to a process whereby contaminants in soil and ponded water adhere to the tires of vehicles departing contaminated areas, such as the former asphalt manufacturing facility property (which was unpaved), and are transported to adjacent streets. Because the T-117 Upland Study Area is now paved, the historical mechanism for the track-out transport of contaminated soil (i.e., track-out) is no longer active. However, active sources such as spills or settled dust could still be contaminating the paved surface and could continue to be tracked out. Filling and dumping6 likely were also primary transport mechanisms by which soil was moved within the T-117 EAA. As discussed in Section 2.1.5.3, shallow soils in the T-117 Upland Study Area and the Adjacent Streets and Residential Yards Study Area 6 For the purpose of the CSM, dumping is similar to filling in that potentially contaminated soil could have been moved within the T-117 EAA and placed on the surface at another location within the facility. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 86 typically consist of fill material, primarily sand and silt, mixed with anthropogenic materials (e.g., asphalt, bricks, rubble, and wood). No specific instances of dumping have been documented in this EE/CA. Because the former asphalt manufacturing facility has been removed, these primary transport mechanisms are no longer active. Dust generation could have also have resulted in the transport of contaminated materials within the upland portions of the T-117 EAA. During dry weather, soil particles from unpaved areas were blown throughout the T-117 EAA. Now that most of the area occupied by the former asphalt manufacturing facility has been paved (except for a margin adjacent to the bank), this mechanism is less prevalent. The stormwater conveyance and discharge primary transport mechanism was relevant historically and continues today. Stormwater runoff from the T-117 Upland Study Area enters the LDW through a network of catch basins that discharge to two outfalls located along the bank. Historically, this mechanism was likely a significant factor in the transport of contaminants from the T-117 Upland Study Area to the T-117 Sediment Study Area. Since early 2000, improvements to the stormwater collection systems at the T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area by the Port and City have significantly controlled the stormwater pathway through infrastructure improvements. The major change was to prevent street runoff in the area around Basin Oil from running across the T-117 Upland Study Area. Routine monitoring and inspections of the stormwater infrastructure are also being conducted to verify the effectiveness of the stormwater controls. Runon to the T-117 Upland Study Area from nearby streets and all runoff from the Adjacent Streets and Residential Yards Study Area is now controlled through the use of catch basins and the redirection of stormwater, primarily to the County's CSS at a maintenance hole on 17th Avenue S and S Donovan Street. Groundwater primary transport mechanisms, including groundwater migration, infiltration, and adsorption/desorption, were also active historically and continue today. The current impact of these mechanisms has been reduced through the removal and capping of soil in the area formerly occupied by the asphalt manufacturing facility, previous removal actions at the T-117 Upland Study Area, and other source control activities both within and outside of the T-117 EAA. As described above, some primary transport mechanisms related to stormwater and groundwater remain active. The potential for these and other transport mechanisms to recontaminate the T-117 Sediment Study Area is discussed in Section 5.2. The media affected by the primary transport mechanisms are designated as secondary sources of contamination (Figure 3-1). Section 3.2 describes the manner in which contaminants from these secondary sources may come in contact with people or animals in specific study areas within the T-117 EAA. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 87 3.2 STUDY AREA-SPECIFIC TRANSPORT MECHANISMS, RECEPTORS, AND EXPOSURE PATHWAYS The following subsections describe the secondary transport mechanisms, receptors, and exposure pathways applicable to each study area in the T-117 EAA. Secondary transport mechanisms are similar to primary transport mechanisms with respect to the physical process (e.g., stormwater discharge), but for the purpose of this discussion, a distinction has been made between the mechanisms that were prevalent when the primary source was active (i.e., primary transport mechanisms) and those that were one step removed (i.e., secondary transport mechanisms). For example, primary transport mechanisms transported contaminants from the former asphalt manufacturing facility to various locations within the T-117 EAA. Now that the former asphalt manufacturing facility is gone, the transport mechanisms are considered to be secondary because media are no longer being contaminated by the original source. This section discusses secondary transport mechanisms, although it should be recognized that each of the primary transport mechanisms discussed in Section 3.1.2 likely influenced the distribution of contaminants in each study area. An exposure pathway focuses on the transport mechanism and exposure routes to a potential receptor. An exposure pathway is considered complete if a chemical can travel from a source to a receptor and is available to that receptor via one or more exposure routes (EPA 1997a, b). The exposure route refers to the way in which the receptor may be exposed (e.g., inhalation, ingestion). Note that exposures of ecological receptors were not evaluated for any of the upland study areas (see Section 2.1.6). For the T-117 Upland Study Area, the current site configuration has less than 0.25 acre of contiguous undeveloped land. As a result, the current site configuration qualified the T-117 Upland Study Area for an exclusion from the TEE (Washington Administrative Code [WAC] 173-340-7491). A simplified TEE conducted for the Adjacent Streets and Residential Yards Study Area also concluded that this study area qualified for the exclusion based on lack of substantial wildlife exposure at the site (Integral 2006c). Consequently, terrestrial ecological receptors are not shown in the CSM (Figure 3-1) or discussed in the rest of the section. Aquatic ecological receptors are included. 3.2.1 T-117 Sediment Study Area The T-117 Sediment Study Area has been contaminated by multiple sources, some of which may be ongoing. The significant transport mechanisms for the T-117 Sediment Study Area include: Erosion of upland surface soil, particularly on the bank Stormwater discharge Groundwater migration and seeps Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 88 Sediment transport within the LDW7 Ecological and human receptors in the T-117 Sediment Study Area could be directly or indirectly exposed to contaminants in soil, sediment, and river water as follows: Ecological Animals using the LDW for habitat, including benthic invertebrates, fish, birds, and mammals Direct exposure Contact with or ingestion of porewater, river water, or sediment Indirect exposure Consumption of benthic invertebrates or fish Human People using the LDW for recreation or food, including fishermen (tribal and recreational), kayakers, clammers, seafood consumers, and children using the intertidal area for recreation Direct exposure Incidental ingestion or dermal contact with sediment, soil, seeps, or river water Indirect exposure Consumption of seafood Other than incidental contact with seep water exiting the bank, there is no direct contact with groundwater in the T-117 EAA (i.e., groundwater is not currently being used for drinking water), nor is there any reasonable expectation of direct contact in the future (see Appendix B for further details). 3.2.2 T-117 Upland Study Area The T-117 Upland Study Area has been contaminated by multiple sources, some of which may be ongoing. Contamination from the T-117 Upland Study Area may also contaminate other study areas. Significant transport mechanisms for the T-117 Upland Study Area include: Erosion of bank soil to surface water and sediment Portions of the upper bank at the T-117 Upland Study Area have been covered with clean gravel or stabilized with a geotextile fabric. Other portions of the upper bank are covered with vegetation, which tends to control the erosion of underlying soil. However, much of the original bank is still exposed to the river; where soil is not stabilized, the potential for erosion of soil particles to the LDW exists. 7 Extensive sediment transport modeling done for the LDW RI/FS indicated that the majority of the sediment transported to the site originates from upriver locations. Sediment transport from downstream locations to the T-117 Sediment Study Area is unlikely to occur in any appreciable quantity (QEA 2008). Additional discussion of LDW sediment transport is provided in Section 5.2.4. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 89 Stormwater outfall discharge Stormwater from the T-117 Upland Study Area enters the LDW through a network of catch basins that discharge to two outfalls located along the river bank. Soil leaching to groundwater PCBs and other hydrophobic chemicals in soil are highly immobile because they are strongly sorbed to organic matter in soils and thus have low partitioning from soil to water (EPA 1990). However, PCBs and other hydrophobic chemicals may migrate in association with colloidal particles or as dissolved components in more mobile substances, such as oil, which have higher miscibility. PCBs and TPH have been detected in both soils and groundwater in T-117 Upland Study Area and thus migration to groundwater from soil may be occurring. Groundwater discharge to LDW surface water and sediment Several active groundwater seeps are present at the base of the shoreline bank and flow out onto the intertidal mudflat. Because the shallow aquifer adjacent to the LDW is tidally influenced, groundwater discharge is a mixture of river water from the preceding high tide and groundwater. Previous groundwater monitoring has detected trace (i.e., just slightly above reporting limits) concentrations of contaminants; thus, the migration from groundwater to LDW surface water and sediment is a potential pathway. Dust generation and transport Most soil at the T-117 Upland Study Area is covered with an asphalt cap. The asphalt cap reduces, if not eliminates, migration pathways such as erosion and windblown dust generation from wind or vehicle traffic migration pathways. Also, any unpaved areas are either capped with clean gravel or heavily vegetated, which helps stabilize the soil and reduces erosion and the potential for fugitive dust generation. However, to the extent that future construction activities disturb bank soils, dust generation and transport could be a transport mechanism. The T-117 Upland Study Area is currently closed to the public (secured by a chain link fence and locked gate) and capped to reduce direct exposure to soil. Therefore, the only current potential receptors in the T-117 Upland Study Area are workers who perform occasional maintenance associated with the 2006 TCRA. These workers could be exposed to contaminants in soil through the following exposure pathways: Direct contact or ingestion with soil Direct contact (incidental ingestion and dermal contact) could occur in areas where soil is uncapped, such as on the bank, or where soil could become exposed during construction. Exposure during construction will be mitigated through the use of personnel protective equipment and engineering controls to prevent contact and access to soil during construction activities. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 90 Inhalation and ingestion of windblown dust in outdoor air A small potential for windblown dust exposure exists from the relatively small areas on the top of the shoreline bank that are only covered with vegetation, or from areas associated with site maintenance or construction activities. Currently, there is no direct contact with groundwater in the T-117 Upland Study Area, nor is there any reasonable expectation of direct contact in the future. This conclusion is supported by the potability evaluation presented in Appendix B. 3.2.3 Adjacent Streets and Residential Yards Study Area Adjacent Streets This section addresses the Adjacent Streets component of this study area; the Residential Yards are discussed in Section 3.2.4. Currently, there are several secondary transport mechanisms for contaminants entering and leaving the Adjacent Streets, as follows: Leaching from surface to subsurface soils Infiltration of rainfall through the soils can leach contaminants from surface soils to subsurface soils in street areas where pavement is not intact or does not exist. Physical disturbance of soils Surface soils along the streets could be exposed via excavation by utility workers. Dust generation and transport Surface soils, or subsurface soils that have been brought to the surface through excavation, could be suspended by the wind or vehicle traffic and deposited on nearby surface soils. Windblown dDust can also be transported by stormwater. Stormwater discharge Most stormwater runoff from streets in this study area is currently carried to the CSS and/ or directly to the LDW from the temporary stormwater storage tanks via occasional emergency overflow events (12 events since 2005). Stormwater from a small portion of Dallas Avenue S flows onto the T-117 Upland Study Area during emergency discharge events (see Section 2.1.3.3), where it is collected by the T-117 storm drainage system. Water in this system is sampled on a regular basis. There has been one detection of total PCBs (0.12 mg/kg) since treatment was discontinued in 2005 (January 2008) (see Section 2.1.3.3) As discussed in Section 3.1.2, improvements to the stormwater collection systems at the Adjacent Streets and Residential Yards Study Area by the City have significantly reduced the volume the stormwater being discharged to the LDW from this area. Soil contamination patterns discussed in Section 2.3 indicate that leaching likely has not resulted in the contamination of groundwater in the Adjacent Streets; thus, this transport mechanism is not considered to be significant for this portion of the study area. The volatilization of VOCs to outdoor and indoor air is also not expected to be a Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 91 significant pathway because the chemicals detected in soil and groundwater from the Adjacent Streets are not volatile (see Section 2.3). People who could be exposed to chemicals in the Adjacent Streets include: Local residents Workers at commercial facilities within the study area Street or utility maintenance workers People could be exposed to contaminants in soil through the following pathways: Direct contact with soil Direct contact (incidental ingestion and dermal contact) could occur in areas where soil is uncapped, such as along street shoulders. Local residents, workers at local industries, or workers performing maintenance on streets could come into contact with surface soils. Residents could also come into contact with these soils when doing maintenance or lawn/yard improvement projects in ROWs. Soils that are capped or paved pose no risk to residents or workers as long as the pavement remains intact. There is a potential for future direct contact if people (e.g., utility workers) excavate areas with contaminated soil. Direct contact with stormwater Stormwater in ROWs may pool in some roadside areas, resulting in the potential exposure of local residents and workers. Inhalation of windblown dust -- Local residents and utility workers digging trenches in the ROWs could inhale and potentially ingest windblown dust generated by wind or vehicle traffic. Workers at local businesses are assumed to spend most of their time indoors, so they will not be exposed in any significant way to windblown dust generated outside. However, dust generated outside of buildings may ultimately be tracked inside, where it could be inhaled and potentially ingested by workers. 3.2.4 Adjacent Streets and Residential Yards Study Area Residential Yards Currently, secondary transport mechanisms for contaminants entering and leaving the Residential Yards include: Dispersal from streets -- Once tracked onto the streets, contaminants may have been dispersed into yards by foot traffic, residential parking, road splash, and dust from the streets. Leaching to subsurface soils Infiltration of rainfall through the soils could potentially leach contaminants from surface soils to subsurface soils. Physical disturbance of soils Subsurface soils could be brought to the surface by residents gardening or undertaking lawn/yard improvement projects. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 92 Dust generation and transport -- Surface soils along the streets could be picked up by the wind or vehicle traffic and deposited onto surface soils in residential yards. Soil contamination patterns discussed in Section 2.3 indicate that leaching likely has not resulted in the contamination of groundwater in the Residential Yards; thus, this transport mechanism is not considered to be significant for this study area. Volatilization of VOCs to outdoor and indoor air is not expected to be of concern because the contaminants detected in the yards are not volatile (see Section 2.3). People who could be exposed to contaminants in residential yards include local residents and utility workers, who could be exposed to contaminated soil through the following pathways: Direct contact with soil -- Direct contact is a potential pathway in areas where soil is uncapped, such as lawns, flowerbeds, and gardens, both as incidental dermal contact or ingestion (including consumption of home-grown produce). Residents could come in contact with subsurface soil through projects that involve digging, including digging through surfaces that may currently be paved or otherwise capped. Residents with pets could also be exposed to soils that may have adhered to the animals' coats. Soils that are capped or paved (e.g., houses, paved driveways) pose no potential risk to residents as long as the surfacing or pavement remains intact. Inhalation of windblown dust Local residents or utility workers digging in yards could inhale and potentially ingest windblown dust generated by wind or vehicle traffic. In addition, residents inhale and potentially ingest dust within households, some of which may have come from soils within the Residential Yards Study Area. The soil ingestion rate used to derive soil CULs includes the ingestion of indoor dust derived from outdoor soil. People using the LDW may be local residents, which would lead to cumulative exposures between the Residential Yards and the T-117 Sediment Study Area. 3.3 CONTAMINANTS OF CONCERN SELECTION PROCESS AND RESULTS This section presents the final COC analysis for the T-117 EAA, which was derived from the COPC analysis presented in the EE/CA Work Plan (Windward et al. 2008) and more recent data. In this analysis, COPCs were first identified based on a comparison of sediment and upland soil data to SLs relevant to the contaminant transport pathways and exposure routes discussed in Section 3.2. COCs for soil and sediment were then selected from the COPC list based on several factors, including detection frequency, age of data, and administrative decisions. The specific rationale used for COC designation is described in more detail by study area below. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 93 SLs are health-protective risk-based values developed for specific media; they are based on specific exposure pathways to specific receptors. Because a single medium may be relevant to multiple exposure pathways (or routes), as demonstrated in the CSM (Figure 3-1), the screening process must explicitly identify the exposure pathways that are evaluated, as summarized in Table 3-1. In some cases, exposure pathways not explicitly addressed in SL development will be further evaluated in Section 4 (as part of the development of RvALs) or in Appendix B (for groundwater). Note that COCs were not identified for sediment for the seafood ingestion pathway noted in Section 3.2.1. Table 3-1. Exposure pathways addressed by screening levels Incorporation of Exposure Pathway for Medium Exposure Pathway Screening Level Development yes, by use of SQS for the protection of benthic direct contact by aquatic organisms invertebrates yes, by use of EPA risk-based goals for residential soil Sediment direct contact by people (to be used as surrogate for sediment) no, to be addressed as part of RvAL development seafood consumption by people (Section 4) direct contact by people (incidental yes, by use of MTCA values for residential soil ingestion and dermal contact) no, to be addressed as part of the development of protection of groundwater quality groundwater RvALs (Section 3.3.3 and Appendix B) no, to be addressed as part of the recontamination protection of sediment quality assessment (Section 5) no, risk assessments conducted for other sites with hydrophobic contaminants (e.g., PCBs along the Soil Housatonic River) suggest that risks associated with consumption of home-grown produce consuming plants grown in soil containing PCBs at the by people concentrations present in Residential Yards are -6 approximately 1 10 , the MTCA target risk level (see Section 3.3.2) no, exposures through the dust inhalation and ingestion pathway are much less than exposures through the soil incidental ingestion pathway (EPA Regions 3, 6, and 9 indoor dust inhalation and ingestion soil PRG for inhalation is 87,000 ng/kg for dioxins and 5,800 ng/kg for PCBs) so screening based on the soil incidental ingestion pathway is protective. yes, by use of ambient water quality criteria to protect Groundwater protection of surface water quality surface water beneficial uses EPA US Environmental Protection Agency MTCA Model Toxics Control Act PCB polychlorinated biphenyl PRG preliminary remediation goal RvAL removal action level SQS sediment quality standards Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 94 3.3.1 Sediment SLs for sediment were developed in consideration of both ecological and human health. Sediment quality standards (SQS) (173-204 WAC) were selected for ecological health. These standards are designed to protect benthic invertebrates in marine sediment. These standards are likely protective of other ecological users of the T-117 Sediment Study Area because of the small size of this area relative to the home ranges of fish, birds, and mammals within the LDW (Windward 2007a). For human health, neither EPA nor Ecology have published risk-based SLs for direct contact with sediment. However, EPA has developed screening values for residential soil exposure, which can be used as an acceptable and health-protective surrogate for the purposes of screening for sediment exposure. The lower of the two values (i.e., SQS and EPA screening values for residential soil) for each chemical were used as SLs for sediment in this assessment (Table 3-2). Table 3-2. Sediment screening levels EPA Screening SQS SQS Value a b Chemical (original units) (mg/kg dw) (mg/kg dw) SL Used fFor EE/CA Metals and Trace Elements Aluminum na na 7,700 7,700 mg/kg Antimony na na 3.1 3.1 mg/kg Arsenic 57 mg/kg 57 0.39 0.37mg39mg/kg Barium na na 1,500 1,500 mg/kg Cadmium 5.1 mg/kg 5.1 7.0 5.1 mg/kg Chromium 260 mg/kg 260 39 39 mg/kg Copper 390 mg/kg 390 310 310 mg/kg Iron na na 5,500 5,500 mg/kg Lead 450 mg/kg 450 40 40 mg/kg Manganese na na 180 180 mg/kg Mercury 0.41 mg/kg 0.41 2.3 0.41 mg/kg Molybdenum na na 39 39 mg/kg Silver 6.1 mg/kg 6.1 39 6.1 mg/kg Thallium na na 0.51 0.51 mg/kg Vanadium na na 39 39 mg/kg Zinc 410 mg/kg 410 2,300 410 mg/kg PAHs 2-Methylnaphthalene 38 mg/kg OC 0.59 31 38 mg/kg OC Acenaphthene 16 mg/kg OC 0.25 340 16 mg/kg OC Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 95 EPA Screening SQS SQS Value a b Chemical (original units) (mg/kg dw) (mg/kg dw) SL Used fFor EE/CA Acenaphthylene 66 mg/kg OC 1.0 na 66 mg/kg OC Anthracene 220 mg/kg OC 3.4 1,700 220 mg/kg OC 110 mg/kg OC 1.7 c Benzo(a)anthracene 0.15 110 mg/kg OC 99 mg/kg OC 1.5 c Benzo(a)pyrene 0.02 99 mg/kg OC Benzo(g,h,i)perylene 31 mg/kg OC 0.48 na 31 mg/kg OC Total benzofluoranthenes 230 mg/kg OC 3.6 c 0.15 230 mg/kg OC cPAH TEQ na 0.015 0.015 mg/kg Chrysene 110 mg/kg OC 1.7 15 110 mg/kg OC c Dibenzo(a,h)anthracene 12 mg/kg OC 0.19 0.02 12 mg/kg OC Dibenzofuran 15 mg/kg OC 0.23 na 15 mg/kg OC Fluoranthene 160 mg/kg OC 2.5 230 160 mg/kg OC Fluorene 23 mg/kg OC 0.36 230 23 mg/kg OC Indeno(1,2,3-cd)pyrene 34 mg/kg OC 0.53 c 0.15 34 mg/kg OC Naphthalene 99 mg/kg OC 1.5 3.90 99 mg/kg OC Phenanthrene 100 mg/kg OC 1.6 na 100 mg/kg OC Pyrene 1,000 mg/kg OC 16 170 1,000 mg/kg OC Total HPAH (calc'd) 960 mg/kg OC 15 na 960 mg/kg OC Total LPAH (calc'd) 370 mg/kg OC 5.7 na 370 mg/kg OC Phthalates BEHP 47 mg/kg OC 0.73 35 47 mg/kg OC BBP 4.9 mg/kg OC 0.076 260 4.9 mg/kg OC Diethyl phthalate 61 mg/kg OC 0.95 4,900 61 mg/kg OC Dimethyl phthalate 53 mg/kg OC 0.82 na 53 mg/kg OC Di-n-butyl phthalate 220 mg/kg OC 3.4 na 220 mg/kg OC Di-n-octyl phthalate 58 mg/kg OC 0.90 na 58 mg/kg OC Other SVOCs 1,2,4-Trichlorobenzene 0.81 mg/kg OC 0.013 8.7 0.81 mg/kg OC 1,2-Dichlorobenzene 2.3 mg/kg OC 0.036 200 2.3 mg/kg OC 1,4-Dichlorobenzene 3.1 mg/kg OC 0.048 2.6 3.1 mg/kg OC 2,4-Dimethylphenol 29 g/kg 0.029 120 0.029 mg/kg 4-Methylphenol 670 g/kg 0.67 na 0.67 mg/kg Benzoic acid 650 g/kg 0.65 24,000 0.65 mg/kg Benzyl alcohol 57 g/kg 0.057 3,100 0.057 mg/kg Hexachlorobenzene 0.38 mg/kg OC 0.0059 0.30 0.38 mg/kg OC Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 96 EPA Screening SQS SQS Value a b Chemical (original units) (mg/kg dw) (mg/kg dw) SL Used fFor EE/CA n-Nitrosodiphenylamine 11 mg/kg OC 0.17 99 11 mg/kg OC Pentachlorophenol 360 g/kg 0.36 3.0 0.36 mg/kg Phenol 420 g/kg 0.42 1,800 0.42 mg/kg Pesticides Dieldrin na na 0.03 0.03 mg/kg Total DDTs na na 1.4 1.4 mg/kg Toxaphene na na 0.44 0.44 mg/kg PCBs d Total PCBs 12 mg/kg OC 0.19 0.22 12 mg/kg OC Dioxins and Furans Dioxin/furan TEQ na na 0.0000045 4.5 ng/kg a SQS values originally presented in units of mg/kg OC were converted to mg/kg dry weight to facilitate comparison with the EPA PRGs that are also in dry weight units. A TOC concentration of 1.55%, reflecting the average TOC concentration in the T-117 Sediment Study Area, was assumed. b Values are from EPA's regional screening values for residential soil (EPA 2009f)(www.epa.gov/reg3hwmd/risk/human/rb-concentration_table/index.htm). Values based on a non- carcinogenic endpoint were divided by 10 to be equivalent to a hazard quotientHQ of 0.1 per EPA Region 10 guidance (EPA 1996b). c SL is based on ecological effects (i.e., SQS) even though human health SL is lower. This cPAH is evaluated as part of the cPAH TEQ parameter. d If the SQS value of 12 mg/kg OC is not used because the TOC value in a sediment sample is either higher or lower than 0.5 to 3.5%, then a site-specific calculation, or "surrogate," can be applied, which results in a value of 0.19 mg/kg dw. BBP butyl benzyl phthalate MTCA Model Toxics Control Act BEHP bis(2-ethylhexyl) phthalate na not applicable cPAH carcinogenic polycyclic aromatic hydrocarbon OC organic carbon DDT dichlorodiphenyltrichloroethane PAH polycyclic aromatic hydrocarbon dw dry weight PCB polychlorinated biphenyl EE/CA engineering evaluation/cost analysis PRG preliminary remediation goal EPA US Environmental Protection Agency SL screening level HPAH high-molecular-weight polycyclic aromatic SQS sediment quality standards hydrocarbon SVOC semivolatile organic compound HQ hazard quotient TEQ toxic equivalent LPAH low-molecular-weight polycyclic aromatic TOC total organic carbon hydrocarbon Bold identifies the concentrations used as the values were identified as SLs. In the first step of the COPC and COC identification process, the SLs presented in Table 3-2 were compared to maximum concentrations in T-117 sediment. Screening was conducted for sediment (surface and subsurface) data collected since 1990. A complete description of all the data management rules used in this step is provided in Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 97 Appendix D.8 As part of the second step, a 5% frequency of detection threshold was selected so that infrequently detected chemicals that may be artifacts in the data as a result of sampling, analytical, or other issues were excluded from further analysis, thereby focusing further evaluation on the contaminants most likely to pose the majority of site risk. This process is consistent with EPA risk assessment guidelines for focusing risk assessments when large numbers of chemicals are present at a site (EPA 1989). In addition, the possibility that these infrequently detected chemicals are from of a unique and localized sources was considered prior to the exclusion of those chemicals as COCs. The final step was included to provide additional refinement of the COC list by considering whether the CSM suggests that a COPC may be related to operations within the T-117 EAA. Table 3-3 lists each sediment COPC and provides a rationale for the COC designation. COPCs were retained as COCs if there was a known or suspected T-117 Upland Study Area source of the chemicals and the concentrations of chemicals in sediment exceeded their respective SLs. The COPCs include total PCBs, several PAHs (including cPAHs), six metals, BEHP, BBP, hexachlorobenzene, dioxins and furans, and phenol. Approximately 50% of the total PCB concentrations in the T-117 Sediment Study Area wasere greater than the SL, suggesting widespread the presence of PCB contamination in the area. Total PCB concentrations were as high as 2,600 mg/kg -OC (51 mg/kg dw), which is more than 200 times the SL. The average total PCB concentration was greater than the SL by a factor of approximately 10. Concentrations of the other COPCs were greater than the applicable SLs much less frequently and by much smaller magnitudes (see Appendix E for all screening results). 8 As part of the data aggregation necessary for screening, data management rules were established for the T-117 EAA; these rules were consistent with those used in the LDW RI/FS. Data management rules ensure consistency among the various datasets used in the screening. Significant Ddata management rules included summation rules for determining total PCBs or PAHs, carbon normalization of dry- weight values, and averaging of replicates, and the application of significant figures. These rules were also used to determine how TEQs for contaminants such as dioxins and furans and cPAHs were calculated. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 98 Table 3-3. Sediment COPCs and COCs Designated as a COC? a COPC Rationale for COC Selection Metals risk estimates from LDW HHRA were well below thresholds of Aluminum no concern risk estimates from LDW HHRA were well below thresholds of Antimony no concern Arsenic yes upland source, one or more recent SL exceedances in sediment risk estimates from LDW HHRA were well below thresholds of Iron no concern risk estimates from LDW HHRA were well below thresholds of Lead no concern risk estimates from LDW HHRA were well below thresholds of Manganese no concern PAHs 2-Methylnaphthalene yes upland source, one or more recent SL exceedances in sediment Acenaphthene yes upland source, one or more recent SL exceedances in sediment Anthracene yes upland source, one or more recent SL exceedances in sediment Benzo(a)anthracene yes upland source, one or more recent SL exceedances in sediment Benzo(a)pyrene yes upland source, one or more recent SL exceedances in sediment Benzo(g,h,i)perylene yes upland source, one or more recent SL exceedances in sediment Total benzofluoranthenes yes upland source, one or more recent SL exceedances in sediment cPAH TEQ yes upland source, one or more recent SL exceedances in sediment Chrysene yes upland source, one or more recent SL exceedances in sediment Dibenzo(a,h)anthracene yes upland source, one or more recent SL exceedances in sediment Dibenzofuran yes upland source, one or more recent SL exceedances in sediment Fluoranthene yes upland source, one or more recent SL exceedances in sediment Fluorene yes upland source, one or more recent SL exceedances in sediment Indeno(1,2,3-cd)pyrene yes upland source, one or more recent SL exceedances in sediment Phenanthrene yes upland source, one or more recent SL exceedances in sediment Total HPAH (calc'd) yes upland source, one or more recent SL exceedances in sediment Total LPAH (calc'd) yes upland source, one or more recent SL exceedances in sediment Phthalates BEHP no single SL exceedance > 10 yrs old BBP no no upland source, single SL exceedance > 10 yrs old Other SVOCs Hexachlorobenzene no no upland source, single SL exceedance > 10 yrs old Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 99 Designated as a COC? a COPC Rationale for COC Selection Phenol yes upland source, one or more recent SL exceedances in sediment PCBs Total PCBs yes upland source, one or more recent SL exceedances in sediment Dioxin and Ffurans upland source, assumed to be present at concentrations above the Dioxin/furan TEQ yes SL, although very few samples have been analyzed a Upland source indicates there is a known or suspected source of the COPC in the T-117 Upland Study Area. BBP butyl benzyl phthalate PAH polycyclic aromatic hydrocarbon BEHP bis(2-ethylhexyl) phthalate PCB polychlorinated biphenyl COC contaminant of concern SL screening level COPC contaminant of potential concern SVOC semivolatile organic compound cPAH carcinogenic polycyclic aromatic hydrocarbon T-117 Terminal 117 HPAH high-molecular-weight polycyclic aromatic hydrocarbon TEQ toxic equivalency quotient LPAH low-molecular-weight polycyclic aromatic hydrocarbon Most of the COPCs were also designated COCs, except for phthalates, hexachlorobenzene, and five of the six metals (all but arsenic). The phthalates and hexachlorobenzene were not designated as COCs because only a single sample result for each contaminant exceeded SLs and the samples was collected more than 10 years ago. Concentrations from all of the more recently collected samples were less than the SLs for these chemicals. Concentrations for aluminum, antimony, iron, lead, and manganese in T-117 sediments were similar to concentrations evaluated in the LDW HHRA for which risk estimates were well below thresholds of concern (i.e., hazard quotient [HQ] of 1 or blood lead concentrations of 10 g/dl). Consequently, these metals were not designated as COCs for the T-117 Sediment Study Area. 3.3.2 Soil This section presents the soil SL development process and the identification of COPCs and COCs for soil for each relevant exposure pathway. As noted in Section 3.2, the terrestrial ecological exposure pathway is not complete. The soil-to-groundwater pathway was directly addressed by evaluating the groundwater concentrations versus relevant SLs in Appendix B (see Section 3.3.3). The soil SLs for direct human contact were based on the MTCA Method B standard formula values, with the exception of lead and TPH. For lead and TPH, the soil SLs were based on the MTCA Method A unrestricted land use CULs (Table 3-4). Method A provides the only applicable SLs for these chemicals. As noted in Table 3-1, SLs for the protection of sediment were not developed. There are no significant transport mechanisms to the T-117 Sediment Study Area for most of the soils present in the T-117 Upland Study Area and the Adjacent Streets and Residential Yards Study Area. Consequently, there is no need to address the protection of sediment quality for most of the soil areas. HoweverUnder Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 100 present conditions, soil in some portion of the T-117 Upland Study Area, particularly on or near the bank, could be transported to the sediment, either now or after the NTCRA is completed through the erosion of bank soil to surface water and sediment via stormwater runoff. However, there are no bank surface soil data available to perform a risk-based screening. After completion of the NTCRA, Because all of these bank or near-bank soils will either be removed or completely isolated so that it cannot be transported to sediment, so as part of the NTCRA, there is no need to conduct additional risk-based screening for the protection of sediment quality. Any current soil areas in the T-117 Upland Study Area that would become part of a future LDW sediment area as the result of the post-NTCRA configuration will meet applicable sediment RvALs at the appropriate point of compliance as discussed in Section 4. Table 3-4. Soil screening levels Concentration (mg/kg) MTCA Method B SL Used for Detected Chemicals Carcinogen Non-Carcinogen EE/CA Metals Aluminum nc nc nc Arsenic 0.67 24 0.67 Barium nc 16,000 16,000 Cadmium nc 80 80 Chromium nc nc nc a Chromium (III) nc 120,000 240 Chromium (VI) nc 240 240 Copper nc 2,960 3,000 b Lead nc nc 250 Mercury nc 24 24 Nickel nc 1,600 1,600 Silver nc 400 400 Zinc nc 24,000 24,000 SVOCs 1-Methylnaphthalene nc nc nc 2-Methylnaphthalene nc 320 320 Acenaphthene nc 4,800 4,800 Acenaphthylene nc nc nc Anthracene nc 24,000 24,000 c Benzo(a)anthracene 0.14 nc nc c Benzo(a)pyrene 0.14 nc nc c Benzo(b)fluoranthene 0.14 nc nc Benzo(g,h,i)perylene nc nc nc Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 101 Concentration (mg/kg) MTCA Method B SL Used for Detected Chemicals Carcinogen Non-Carcinogen EE/CA c Benzo(k)fluoranthene 0.14 nc nc Benzofluoranthenes nc nc nc Benzoic acid nc 320,000 320,000 Benzyl alcohol nc 24,000 24,000 BEHP 71 1,600 71 BBP nc 16,000 16,000 c Chrysene 0.14 nc nc c Dibenzo(a,h)anthracene 0.14 nc nc Dibenzofuran nc 160 160 Dimethyl phthalate nc 80,000 80,000 Fluoranthene nc 3,200 3,200 Fluorene nc 3,200 3,200 c Indeno(1,2,3-cd)pyrene 0.14 nc nc Naphthalene nc 1,600 1,600 Phenanthrene nc nc nc Pyrene nc 2,400 2,400 cPAH TEQ 0.14 nc 0.14 PCBs Total PCBs 0.50 nc 0.50 TPH b Total diesel-range hydrocarbons nc nc 2,000 b Gasoline-range hydrocarbons nc nc 100 Dioxin and Furans Dioxin/furan TEQ 0.000011 nc 0.000011 a Hexavalent chromium criterion used because chromium speciation was not performed. b Value from MTCA Method A for soil for unrestricted land use. c Individual carcinogenic PAHs were evaluated only as part of the cPAH TEQ. BBP butyl benzyl phthalate SL screening level BEHP bis(2-ethylhexyl) phthalate SVOC semivolatile organic compound cPAH carcinogenic polycyclic aromatic hydrocarbon TEQ toxic equivalency quotient EE/CA engineering evaluation/cost analysis TPH total petroleum hydrocarbons MTCA Model Toxics Control Act TSCA Toxic Substances Control Act nc no criteria VOC volatile organic compound PCB polychlorinated biphenyl Bold values were identified as SLs. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 102 3.3.2.1 T-117 Upland Study Area Similar to the approach used to evaluate the T-117 Sediment Study Area, the first step of the COPC and COC identification process was to compare the SLs presented in Table 3-4 with maximum concentrations in T-117 Upland Study Area soil samples. All available T-117 Upland Study Area soil data were evaluated in the screening process, except data associated with soil that has been removed as part of the 1999 and 2006 TCRAs. The screening process included a general statistical review of detected soil chemicals. Appendix E details and summarizes the T-117 Upland Study Area soil screening process. For the second step, a 5% frequency of detection threshold was selected so that infrequently detected chemicals in the dataset were excluded from further analysis, thereby focusing further evaluation on the contaminants most likely to pose the majority of site risk. This process is consistent with EPA risk assessment guidelines for focusing risk assessments when large numbers of chemicals are present at a site (EPA 1989). Table 3-5 summarizes the soil COPCs and COCs for the T-117 Upland Study Area, which include total PCBs, TPH, cPAH, dioxins/furans, and arsenic. Approximately 58% of the detected total PCB concentrations were greater than the SL, suggesting widespread PCB contamination in this area. The maximum detected total PCB concentration was over 8,000 times the SL. The average PCB concentration was greater than the SL by a factor of approximately 60. Table 3-5. Soil COPCs and COCs in the T-117 Upland Study Area Designated as COPC a COC? Rationale for COC Selection Arsenic yes one or more recent SL exceedances in soil Total PCBs yes one or more recent SL exceedances in soil TPH (diesel range) yes one or more recent SL exceedances in soil cPAH TEQ yes one or more recent SL exceedances in soil Dioxin/furan TEQ yes one or more recent SL exceedances in soil COC contaminant of concern COPC contaminant of potential concern cPAH carcinogenic polycyclic aromatic hydrocarbons PCB polychlorinated biphenyl SL screening level TEQ toxic equivalent TPH total petroleum hydrocarbons More than 50% of the detected concentrations of cPAHs, dioxins and furans, and arsenic exceeded the applicable SLs. Approximately 17% of detected TPH Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 103 concentrations exceeded the applicable SL. These contaminants were thus retained as COCs because they were detected in more than 5% of the samples and exceeded applicable SLs. 3.3.2.2 Adjacent Streets and Residential Yards Study Area Adjacent Streets Soil investigations conducted in the Adjacent Streets since 2005 were described in Section 2.3.3. All available soil data, including both discrete samples (surface samples and borings) in streets and road shoulders and multi-incrementMIS samples collected along road shoulders in 2009, were included in the evaluation. Data were not included for catch basin solids9 or for samples collected from areas removed during independent cleanup actions or from areas where more recent MIS was conducted. Table 3-6 summarizes the soil COPCs and COCs designations for the Adjacent Streets,. COPCs which include total PCBs, TPH, cPAH, dioxins and furans, and arsenic.arsenic, total PCBs, TPH, cPAHs, and dioxins and furans. Approximately 30% (51% for Adjacent Streets and 14% for Residential Yards) of the detected total PCB concentrations were greater than the SL, suggesting widespread PCB contamination in this area. The maximum detected total PCB concentration was over 960 times the SL. The average PCB concentration was greater than the SL by a factor of approximately 14. PCBs were thus retained as COCs because they were detected in more than 5% of the samples and exceeded applicable SLs. Table 3-6. Soil COPCs and COCs for Adjacent Streets COPC Designated as a COC? Rationale for COC Selection Total PCBs yes upland source, SL exceedances yes, in locations where Dioxin/furan TEQ PCB concentrations potential upland source, SL exceedances a exceeded the PCB RvAL administrative decision by EPA based on lack of clear evidence Arsenic no that T-117 Upland Study Area was significant source of COPC to Adjacent Streets administrative decision by EPA based on lack of clear evidence TPH no that T-117 Upland Study Area was significant source of COPC to Adjacent Streets administrative decision by EPA based on lack of clear evidence cPAH TEQ no that T-117 Upland Study Area was significant source of COPC to Adjacent Streets a Per EPA directive. COC contaminant of concern SL screening level COPC contaminant of potential concern T-117 Terminal 117 9 Samples of catch basin solids were not considered to be soils for this streamlined risk assessment and were not screened. Catch basin data were presented in Section 2 and are discussed in Section 5 with respect to sediment recontamination potential. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 104 cPAH carcinogenic polycyclic aromatic hydrocarbons TEQ toxic equivalent EPA US Environmental Protection Agency TPH total petroleum hydrocarbons PCB polychlorinated biphenyl Approximately 75% of dioxins and furans exceeded the applicable SLs (70% for Adjacent Streets and 79% for Residential Yards). Dioxins and furans were thus retained as COCs because they were detected in more than 5% of the samples and exceeded applicable SLs. However, they were only designated as COCs in areas where they were co-located with total PCB concentrations above the selected PCB RvAL, per administrative direction by EPA (2009a). This decision was based on an assumption that a minor portion of the dioxins and furans in the Adjacent Streets and Residential Yards Study Area may be associated with PCBs from asphalt manufacturing facility operations. In Adjacent Streets, approximately 83% of cPAH, 14% of TPH, and 100% of arsenic detected values exceeded the applicable SLs. However these were not designated as COCs for the Adjacent Streets and Residential Yards Study Area, per administrative direction by EPA (2009a). EPA's decision was based on a lack of clear evidence that the T-117 Upland Study Area was a significant source of these contaminants to the Adjacent Streets. Although TPH and cPAH are expected to be associated with PCB- containing oil, they are also common urban contaminants (e.g., associated with asphalt paving). The limited arsenic concentration data available for the Adjacent Streets were within the range of background concentrations (Ecology 1994c) or were collected from areas identified for soil removal. Based on the forensic work completed by the Dioxin Technical Workgroup and their 2008 and 2009 findings (Appendix M), EPA made the determination that the former asphalt manufacturing facility operations are likely not the source of the majority of the dioxins and furans detected in the Adjacent Streets and Yards Study Area, and that the source of the dioxins and furans is as yet undetermined. However, based on an assumption that a minor portion of the dioxins and furans in the Adjacent Streets and Residential Yards Study Area may be associated with PCBs from asphalt manufacturing facility operations, EPA directed dioxins and furans be designated as COCs where they are colocated with total PCBs above the action level in the Adjacent Streets and Residential Yards Study Area. TPH, cPAHs, and Arsenic -TPH, cPAHs, and arsenic were not designated as COCs for the Adjacent Streets and Residential Yards Study Area, per administrative direction by EPA (2009a). EPA's decision was based on a lack of clear evidence the T-117 Upland Study Area was a significant source of these contaminants to the Adjacent Streets. While TPH and cPAH are expected to be associated with PCB-containing oil, they are also common urban contaminants (e.g., associated with asphalt paving). The limited arsenic concentration data Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 105 available for the Adjacent Streets were within the range of background concentrations (Ecology 1994c) or were collected in areas identified for soil removal. 3.3.2.3 Adjacent Streets and Residential Yards Study Area Residential Yards Following removal actions in 2004 and 2005, additional soil sampling was conducted in yards within the Adjacent Streets and Residential Yards Study Area in 2008 and 2009. Samples were analyzed for total PCBs and dioxins and furans (Ecology analyzed splits of a subset of the 2009 samples for dioxins and furans). Both total PCBs and dioxins and furans were selected as COPCs and COCs in this area (Table 3-7). The detailed screening results are provided in Appendix E. Table 3-7. Soil COPCs and COCs for Residential Yards Designated COPC as a COC? Rationale for COC Selection Total PCBs yes upland source, SL exceedances Dioxin/furan TEQ yes upland source, SL exceedances COC contaminant of concern COPC contaminant of potential concern PCB polychlorinated biphenyl SL screening level TEQ toxic equivalent TPH total petroleum hydrocarbons As discussed in the previous section, EPA directed that dioxins and furans be designated as COCs where they are co-located with total PCB concentrations above the action level in the Adjacent Streets and Residential Yards Study Area (see Section 4.3.32.2). 3.3.3 Groundwater As noted in the introduction to Section 3, groundwater was not explicitly addressed in the streamlined risk assessment. However, because protecting groundwater quality is an important goal of the NTCRA, technical analyses were conducted to address groundwater. Two of the analyses presented in Appendix B that pertain to groundwater potability and the identification of COCs for groundwater are summarized briefly below. 3.3.3.1 Groundwater potability The potential for groundwater to be used as a drinking water source is important for the evaluation of site-specific potential groundwater exposure pathways. A full potability evaluation that details the regulatory basis for a non-potable designation for groundwater in the vicinity of the T-117 Upland Study Area is provided in Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 106 Appendix B. The area suggested for application of the non-potability designation is shown on Map 3-1. This area includes the T-117 Uplands Study Area and portions of the Adjacent Streets Study area near Basin Oil. Groundwater beneath other areas of the Adjacent Streets and Residential Yards Study Area was assumed to be potable. The non-potable designation for groundwater is reflected by the absence of the direct contact with groundwater exposure pathway in Section 3.2.2. EPA's policy is to defer to a "State's determination of current and future groundwater uses" provided that the state's program is recognized in the Comprehensive State Ground Water Protection Program (CSGWPP) (EPA 2009d). The State of Washington's potability determination under MTCA is recognized by the CSGWPP; therefore, MTCA is the guiding regulation for this potability determination. Based on MTCA, groundwater in the vicinity of the T-117 Upland Study Area is not potable as summarized below: EPA's policy is to defer to a "State's determination of current and future groundwater uses" provided that the state's program is recognized in the Comprehensive State Ground Water Protection Program (CSGWPP) (EPA 2009d). The State of Washington's potability determination under MTCA is recognized by the CSGWPP; therefore, MTCA is the guiding regulation for this potability determination. Based on MTCA, groundwater in the vicinity of the T-117 Upland Study Area is not potable as summarized below: Groundwater in the vicinity of the T-117 Upland Study Area does not flow into a source of drinking water. Groundwater flows directly into the adjacent portion of the LDW, which has been deemed by the State of Washington as being unsuitable for domestic use. Groundwater in the vicinity of the T-117 Upland Study Area could not become a source of drinking water and does not flow into a water body that could become a source of drinking water. Groundwater exceeds the state standard for specific conductance because of its location along the LDW and the upwelling of saline deep groundwater along a localized bedrock outcropping. As stated above, the LDW, as determined by the State of Washington, is not suitable for domestic use. In addition to the MTCA non-potability determination, local codes prohibit the construction of drinking water wells in the vicinity of the T-117 EAA: Based on the King County Board of Health (KCBOH) regulations and King County Code sections cited below, a drinking water well would be prohibited at the site. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 107 KCBOH Code 12.32.010.D requires that lots created by subdivision, short subdivision, re-zone, or lot line adjustment that were created after 1972 and that are less than 5 acres must be connected to a public water supply. KCBOH Code 12.32.010.A requires that property owners undertaking "new development" must connect to available public water supply. "Development" is defined broadly to include "land utilization" and according to County staff would itself include any proposal to install a groundwater extraction well, which effectively prohibits installation of such a well. King County Code 13.24.140 (King County Water and Sewer Comprehensive Plan contained in Title 13 of the code) applies to properties outside the City and requires all new development within the Urban Growth Area to be served by the appropriate existing Group A water supplier, unless service cannot be timely and reasonably provided. Therefore, because all of the properties in the vicinity of the T-117 EAA are served by a public water supply, any new development at or near the T-117 EAA must also be connected to this supply. KCBOH Code 12.24.010A states that the drinking water supply must come from the "highest quality source feasible." The highest quality source available at the T-117 EAA is the SPU water supply from the Cedar River Watershed. KCBOH Code 12.24.010(C) specifies the minimum setbacks for drinking water wells, which are 100 ft from surface water, roads, utilities, and buildings. The T--117 Upland Study Area is a narrow piece of land (approximately 200 feet wide) situated between Dallas Avenue S and the LDW. These KCBOH code sections reaffirm state regulations found at WAC 246-290-130(1) and WAC 246-290-135(2)(b). 3.3.3.2 Groundwater COCs Similar to the process discussed above for sediment and soil COCs, SLs were developed for groundwater. With the exception of TPH, SLs were based on ambient water quality criteria to protect surface water beneficial uses. The TPH SL was based on MTCA Method A. These SLs are re-evaluated in Section 4 as part of the RvAL development to ensure the concentrations are also sufficiently low to prevent sediment recontamination. There are no drinking water wells in the T-117 EAA, and as indicated in the previous section, future construction of drinking water wells is prohibited within the T-117 EAA Upland and Adjacent Streets and Residential Yards Study Areas. In addition, as discussed in Section 2.3.4.2 and Appendix B.4, the presence of groundwater contamination beneath the Adjacent Streets Study Area due to former T-117 operations is unlikely. As a result, groundwater COCs and RvALs have not been developed for the Adjacent Streets and Residential Yards Study Area. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 108 Table 3-8B-1, of Appendix B, includes a summary of the selected groundwater SLs. Screening was conducted using groundwater chemistry results from monitoring wells sampled since 2003. The groundwater COPCs included arsenic, copper, silver, total PCBs, TPH, cPAH TEQ, and BEHP (Table 3-89). All but copper COPCs were designated as COCs. Under WAC 173-340-730(5)(c), copper was not retained as groundwater COC because concentrations in the vicinity of the T-117 Upland Study Area are not significantly different than the site specific background populations. Copper concentrations in upgradient wells (wells MW-01, and MW-09 through MW- -13) were compared to concentrations in T-117 Upland Study Area wells (wells MW-02 through MW-08R). Copper concentrations between these two data sets are not significantly different, and therefore, concentrations at the T-117 Upland Study Area wells are considered to be background values (Appendix B). Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 109 Table 3-8. Groundwater screening levels Concentration (g/L) a Aquatic Life Criteria Washington State WQC National AWQC Surface Water Criteria Human Health Freshwater Marine Freshwater Marine MTCA Method B Criteria for All Detected Consumption Non- SL Used b c b c d e d e f Chemicals Chronic Acute Chronic Acute CCC CMC CCC CMC of Organisms Carcinogen Carcinogen for EE/CA Metals and Trace Elements g, h Arsenic 190 360 36 69 150 340 36 69 0.14 0.098 18 0.14 Cadmium 1.0 3.7 9.3 42 0.25 2.0 8.8 40 nc nc 20 0.25 Chromium (hexavalent) 10 15 50 1,100 11 16 50 1,100 nc nc 486 10 Chromium (trivalent) 180 550 nc nc 74 570 k nc nc nc nc 243,056 10 Copper 11 17 3.1 4.8 9 13 3.1 4.8 nc nc 2,665 3.1 Nickel 160 1,400 8.2 74 52 470 8.2 74 4,600 nc 1,103 8.2 Silver nc 3.4 nc 1.9 nc 3.2 nc 1.9 nc nc 25,926 1.9 Zinc 100 110 81 90 120 120 81 90 26,000 nc 16,548 81 TPH j Total TPH nc nc nc nc nc nc nc nc nc nc nc 500 PCBs g Total PCBs 0.014 2 0.03 10 0.014 nc 0.03 nc 0.000064 0.00011 nc 0.000064 PAHs 1-Methylnaphthalene nc nc nc nc nc nc nc nc nc nc nc nc i Acenaphthene nc nc nc nc nc nc nc nc 990 nc 643 990 l Anthracene nc nc nc nc nc nc nc nc 40,000 nc 25,926 40,000 g Benzo(a)anthracene nc nc nc nc nc nc nc nc 0.018 0.030 nc 0.018 g Benzo(a)pyrene nc nc nc nc nc nc nc nc 0.018 0.030 nc 0.018 Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 110 Concentration (g/L) a Aquatic Life Criteria Washington State WQC National AWQC Surface Water Criteria Human Health Freshwater Marine Freshwater Marine MTCA Method B Criteria for All Detected Consumption Non- SL Used b c b c d e d e f Chemicals Chronic Acute Chronic Acute CCC CMC CCC CMC of Organisms Carcinogen Carcinogen for EE/CA g Benzo(b)fluoranthene nc nc nc nc nc nc nc nc 0.018 0.030 nc 0.018 g Benzo(k)fluoranthene nc nc nc nc nc nc nc nc 0.018 0.030 nc 0.018 g Chrysene nc nc nc nc nc nc nc nc 0.018 0.030 nc 0.018 g Dibenzo(a,h)anthracene nc nc nc nc nc nc nc nc 0.018 0.030 nc 0.018 i Fluoranthene nc nc nc nc nc nc nc nc 140 nc 90 140 i Fluorene nc nc nc nc nc nc nc nc 5,300 nc 3,457 5,300 g Indeno(1,2,3-cd)pyrene nc nc nc nc nc nc nc nc 0.018 0.030 nc 0.018 Naphthalene nc nc nc nc nc nc nc nc nc nc 4,938 4,938 Phenanthrene nc nc nc nc nc nc nc nc nc nc nc nc l Pyrene nc nc nc nc nc nc nc nc 4,000 nc 2,593 4,000 g cPAH TEQ nc nc nc nc nc nc nc nc 0.018 0.030 nc 0.018 BTEX Xylene nc nc nc nc nc nc nc nc nc nc nc nc Phthalates g BEHP nc nc nc nc nc nc nc nc 2.2 3.6 399 2.2 SVOCs l Phenol nc nc nc nc nc nc nc nc 1,700,000 nc 1,111,111 1,700,000 VOCs 1,1,1-Trichloroethane nc nc nc nc nc nc nc nc nc nc 416,667 416,667 Acetone nc nc nc nc nc nc nc nc nc nc nc nc Chlorobenzene nc nc nc nc nc nc nc nc 1,600 nc 5,034 1,600 Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 111 Concentration (g/L) a Aquatic Life Criteria Washington State WQC National AWQC Surface Water Criteria Human Health Freshwater Marine Freshwater Marine MTCA Method B Criteria for All Detected Consumption Non- SL Used b c b c d e d e f Chemicals Chronic Acute Chronic Acute CCC CMC CCC CMC of Organisms Carcinogen Carcinogen for EE/CA cis-1,2-Dichloroethene nc nc nc nc nc nc nc nc nc nc nc nc g l Tetrachloroethene nc nc nc nc nc nc nc nc 3.3 0.39 836 3.3 g l Trichloroethene nc nc nc nc nc nc nc nc 30 6.7 71 30 Dioxin/Furans -9 g -9 g 2,3,7,8-TCDD TEQ nc nc nc nc nc nc nc nc 5.0 x 10 nc nc 5.0 x 10 a Aquatic life criteria are based on dissolved concentrations for metals (except mercury) and total concentrations for mercury and organic compounds. b Chronic criteria are 4-day average concentrations not to be exceeded more than once every 3 years on the average, with the exception of pesticide and PCB concentrations, which are 24-hr average concentrations not to be exceeded at any time. c Acute criteria are 1-hr average concentrations not to be exceeded more than once every 3 years on average, with the exception of silver and pesticide concentrations, which are instantaneous concentrations not to be exceeded at any time, or the PCB concentration, which is a 24-hr average concentration not to be exceeded at any time. d The CCC is defined as an estimate of the highest concentration of a chemical in surface water to which an aquatic community can be exposed indefinitely without resulting in an unacceptable effect. e The CMC is defined as an estimate of the highest concentration of a chemical in surface water to which an aquatic community can be exposed briefly without resulting in an unacceptable effect. f Washington State and national water quality criteria for the protection of human health are the same. Human health criteria are based on dissolved concentrations for all chemicals for marine water for ingestion of only organisms only (not water). g -6 Criteria are based on 10 excess cancer risk for carcinogenic chemicals. h WQC represents the inorganic fraction of arsenic. I The criteria for pentachlorophenol are pH-dependent; a pH of 7 was assumed. j Criteria for MTCA Method A for groundwater. k Hexavalent chromium criterion was used because chromium speciation was not performed. l SL was selected based on MTCA Method B CUL site-specific calculated value is higher than MTCA Method B default value. AWQC ambient water quality criteria EE/CA engineering evaluation/cost analysis SVOC semivolatile organic compound BEHP bis(2-ethylhexyl) phthalate MTCA Model Toxics Control Act TEQ toxic equivalent Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 112 BTEX benzene, toluene, ethylbenzene, and xylene nc no criteria TCDD tetrachlorodibenzo-p-dioxin CCC criteria continuous concentration PAH polycyclic aromatic hydrocarbon TPH total petroleum hydrocarbons CMC criteria maximum concentration PCB polychlorinated biphenyl VOC volatile organic compound cPAH carcinogenic polycyclic aromatic hydrocarbon SL screening level WQC water quality criteria CUL cleanup level Bold identifies values calculated using a hardness value of 100 mg/L. In most cases, the Washington State WQC and national AWQC are the same. In cases where they are different, the lower of the two values is used. Gray-shaded values were identified as SLs. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 113 The site-specific background groundwater dissolved copper concentration was 5 g/L based on the 90th percentile. This concentration is lower than, but consistent, with, the background groundwater dissolved copper concentration (8 g/L, as established by EPA) calculated for the Boeing Plant 2 site (Environmental Partners 2006). Greater than 50% of the detected sample concentrations exceed the SLs for silver, total PCBs, TPH, and cPAH TEQ. Approximately 43% of the detected concentrations exceed the BEHP screening values. Approximately 19% of the detected sample concentrations exceed the SLs for arsenic. However, 43% of the concentrations reported below the laboratory reporting limits for arsenic also exceed the SL. All of these compounds have a detected frequency greater than 5%. Table 3-98. Groundwater COPCs and COCs Designated as COPC a COC? Rationale for COC Selection Arsenic yes one or more recent SL exceedance in groundwater concentrations less than or equal to upgradient Copper no background concentration Silver yes one or more recent SL exceedance in groundwater Total PCBs yes one or more recent SL exceedance in groundwater TPH yes one or more recent SL exceedance in groundwater cPAH TEQ yes one or more recent SL exceedance in groundwater BEHP yes one or more recent SL exceedance in groundwater BEHP bis(2-ethylhexyl) phthalate COC contaminant of concern COPC contaminant of potential concern cPAH carcinogenic polycyclic aromatic hydrocarbon PCB polychlorinated biphenyl SL screening level TPH total petroleum hydrocarbons 3.3.4 RAA contaminants According to the SOW (EPA 2007c), in addition to COCs selected for each of the T-117 EAA Study Areas discussed in Section 3.3.2 and summarized in Section 3.3.3, contaminants found on the Basin Oil property or Marina that pose a potential for post--NTCRA sediment recontamination must be identified. This section presents the results of this identification analysis. Basin Oil groundwater and soil data (Ecology 2009b) were screened using the SLs developed for the T-117 EAA in Appendix B and Section 3.3.2, respectively. Concentrations of arsenic, total PCBs, BEHP, copper, TPH, nickel, cPAHs, Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 114 ethylbenzene, xylenes, and carbazole were greater than SLs in soil and groundwater upgradient of the T-117 Upland Study Area. Except for nickel, xylenes, carbazole, and ethylbenzene, these contaminants were already included as COCs for the T-117 EAA. Specific results were as follows: Monitoring wells downgradient of the Basin Oil property, and upgradient of the T-117 Upland Study Area, had SL exceedances for arsenic (MW-01 and MW-11), copper (MW-01 and MW-10), total PCBs (MW-01), BEHP (MW-01, MW-9, MW-10, and MW-11), and TPH (MW-10). Monitoring wells upgradient of Basin Oil property had arsenic concentrations greater than the SL (MW-12, MW-13). Concentrations of arsenic, TPH (lube oil and gas), cPAHs, total PCBs, ethylbenzene, and xylenes in surface soils were greater than SLs. Arsenic, cPAH, and carbazole concentrations in surface soil samples from upgradient monitoring wells were greater than their SLs. The total PCB concentration in one 12.5-ft-deep soil sample (BSB-3) was greater than the SL. With respect to the Marina, as discussed in Section 2.4.2, metals, total PCBs (quantified as Aroclor 1254), pesticides, PAHs, TPH, and VOCs were detected above SLs in soil samples. Of the contaminants with concentrations greater than SLs in soil, only total PCBs (quantified as Aroclor 1260) had concentrations greater than the SQS in Marina sediment. The chemicals identified in these RAAs at concentrations above SLs will be incorporated into the analysis presented in Section 5.2 of the recontamination potential from these two areas (Basin Oil property and the Marina). 3.3.5 Summary of streamlined risk assessment This section provides an overview of the pathways, receptors, and COCs for each of the T-117 EAA Study Areas discussed in this section. A summary of the exposure pathways and receptors identified in the streamlined risk assessment is presented in Table 3-910. A summary of the COCs identified in each T-117 study area is presented in Table 3-1011. Total PCBs and dioxins and furans were identified as COCs in all study areas. RvALs for COCs identified for sediment and soil are presented in Section 4. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 115 Table 3-910. Summary of exposure pathways and receptors identified in the streamlined risk assessment Sediment Soil Groundwater T-117 T-117 Exposure Sediment Upland Adjacent Residential T-117 Upland Pathways Receptors Study Area Study Area Streets Yards Study Area Aquatic Organisms benthic X X invertebrates Ingestion, dermal mammals X contact fish X X birds X mammals - Inhalation birds - People kayakers X X fishermen X X Ingestion, dermal clammers X X contact beachgoers X X residents X X workers X X X X X kayakers fishermen clammers Inhalation beachgoers residents X X X workers X X X People and Animals fish X Seafood birds X cConsumption mammals X people X T-117 Terminal 117 Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 116 Table 3-1011. Summary of COCs identified in the streamlined risk assessment Sediment Soil Groundwater T-117 T-117 Sediment Upland Adjacent Residential T-117 Upland COCs Study Area Study Area Streets Yards Study Area Metals Arsenic X X X Copper X Silver X PAHs 2-Methylnaphthalene X Acenaphthene X Anthracene X Benzo(a)anthracene X Benzo(a)pyrene X Benzo(g,h,i)perylene X Total benzofluoranthenes X cPAH TEQ X X X Chrysene X Dibenzo(a,h)anthracene X Dibenzofuran X Fluoranthene X Fluorene X Indeno(1,2,3-cd)pyrene X Phenanthrene X Total HPAH (calc'd) X Total LPAH (calc'd) X TPH Diesel- and lube oil-range X X hydrocarbons Other SVOCs BEHP X Phenol X PCBs Total PCBs X X X X X Dioxins and Furans Dioxin/furan TEQ X X X X Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 117 BEHP bis(2-ethylhexyl) phthalate PAH polycyclic aromatic hydrocarbon COC contaminant of concern PCB polychlorinated biphenyl cPAH carcinogenic polycyclic aromatic hydrocarbon SVOC semivolatile organic compound HPAH high-molecular-weight polycyclic aromatic hydrocarbon T-117 Terminal 117 LPAH low-molecular-weight polycyclic aromatic hydrocarbon TEQ toxic equivalent OC organic carbon TPH total petroleum hydrocarbons Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 118 4 Identification of Removal Action Scope, Goals, and Objectives This section presents the NTCRA scope, goals, and objectives for the T-117 EAA in accordance with EPA's Guidance on Conducting Non-Time-Critical Removal Actions Under CERCLA (EPA 1993) and discusses the development of RvALs for the T-117 EAA. This section includes: A description of specific scope, goals, and objectives for the T-117 EAA Regulatory requirements and guidance, including applicable or relevant and appropriate requirements (ARARs) Definition Development of of RvALs, which are defined as site- specific removal action levels Presentation of the numerical RvALs for each medium, including sediment, soil, and groundwater, which wereRvALs selected to meet these goals, objectives, and ARARs Final removal boundaries for each study area, based on the RvALs for each mediumBoundaries for the removal actions in the study areas 4.1 NTCRA SCOPE, GOALS, AND OBJECTIVES The scope of this NTCRA includes the removal (or removal and capping) of sediment and the removal of soil to meet RvALs at the appropriate points of compliance. This NTCRA is designed to address sediment COCs within the T-117 Sediment Study Area and soil COCs in the T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area. The goal of the NTCRA for the T-117 EAA is to reduce the current and future exposure of ecological and human receptors to COCs. Reasonably anticipated future land uses include various non-industrial uses such as river and/or shoreline aquatic habitat and upland habitat, public access and recreation, residential and commercial uses, as well as industrial uses. Consistent with MTCA, unrestricted land use will be evaluated. These potential future site uses were considered in the selection of RvALs. In summary, the removal action objectives (RAOs) for the T-117 EAA includeare: Sediment Human Health seafood consumption. Reduce human health risks associated with the consumption of resident LDW fish and shellfish by to reducing sediment concentrations of COCs to protective levels. Human Health direct contact. Reduce human health risks associated with exposure to COCs through direct contact with sediments and incidental Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 119 sediment ingestion by reducing sediment concentrations of COCs to protective levels. Ecological Health benthic. Reduce toxicity to benthic invertebrates by reducing sediment concentrations of COCs to comply with SMS. Ecological Health seafood consumption. Reduce risks to crabs, fish, birds and mammals from exposure to COCs by reducing concentrations of COCs in sediment to protective levels. Soil Sediment Protection. Reduce PCB concentrations in upland soils to ensure protection of sediments. Sediment removal and/or capping to be protective of: Biological resources Human health Direct contact tribal clamming, netfishing, beach play Indirect contact fish consumption Soil removal to be protective of: Human health direct contact, incidental ingestion Ecological health Sediment quality Groundwater quality Because of the residential land use within the T-117 EAEA, EPA has established that the RAOs for the T-117 EAA must consider RvALs associated with MTCA-defined unrestricted land use in the upland portions of the site (Appendix A). Groundwater at the T-117 EAA has been evaluated and groundwater action levels have been developed to ensure that groundwater quality at the point of discharge to LDW surface water and sediment will not result in the recontamination of sediment (Section 5.2) or in the contamination of water at levels that could pose risks through seafood ingestion (Appendix B). Specific removal actions for soil and sediment must meet the RAOs if they are to be considered and selected for implementation. The development and selection of specific removal actions must also consider reasonably anticipated future land uses. Selected RvALs must be sufficient to allow for the entire range of these potential uses. In addition, any future development projects must comply with land-use regulations (development, environmental, zoning) and the associated permitting procedures and requirements. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 120 Selected RvALs for the T-117 Upland Study Area are also expected to be sufficiently protective to allow for possible future habitat development, as well as other final site uses including commercial site uses (e.g., restroom facilities). The Port is examining habitat restoration opportunities within all or a portion of the T-117 Sediment Study Area and the T-117 Upland Study Area. As part of this potential site use, locations within the T-117 Upland Study Area may be converted to aquatic habitat; portions of the upland soil may become located within or beneath a portion of the intertidal sediment. In addition, any sediment removal action that includes excavation or dredging will expose new sediments within the aquatic area. To address ensure the protectiveness of sediment, these potential future configurations, the specific cleanup objective of any T-117 removal action that creates generates new sediment surfaces will be to achieve contaminant concentrations at or below the sediment RvALs to the prescribed depth of compliance. Furthermore, an additional cover or cap (e.g., clean, imported backfill material) may be placed over sediment areas at certain locations to meet the RvALs to the prescribed depth and/or to ensure the permanence of the removal action. If the removal action can seamlessly transition to habitat restoration, upland areas that would be converted into intertidal areas would be completed in accordance with the sediment NTCRA (i.e., meet the sediment RAOs). Section 7 of this EE/CA describes removal action alternatives that are compatible with habitat restoration. It is expected that the existing aquatic sediment portion of the site will remain aquatic and will be subject to the RvALs defined for the Sediment Study Area. The future land use for the Adjacent Streets and Residential Yards Study Area is expected to retain a combination of residential and commercial uses. Current City zone designations for this study area include Commercial 1 (C1) and Neighborhood Commercial 3 (NC3) (City of Seattle 2007a). The City's Comprehensive Plan future land use map shows the Adjacent Streets and Residential Yards Study Area as commercial/mixed use and industrial (City of Seattle 2007b). Street improvements conducted in conjunction with this NTCRA will be consistent with current codes for street paving width and curb, gutter, and sidewalk installation. 4.2 REGULATORY REQUIREMENTS AND GUIDANCE Potential ARARs and guidance for removal activities within the LDW Superfund Site were identified in the LDW Phase 1 RI (Windward 2003a).10 Most of these regulations are relevant to the scope, goals, objectives, and development of RvALs for the NTCRA described in this EE/CA, as well as the detailed evaluation of removal action alternatives (Section 8.2.3 and Table 8-1) and eventual NTCRA implementation. A listing and description these requirements and guidance, including CERCLA, TSCA, MTCA, SMS, and other requirements to be considered for the T-117 NTCRA, are provided in Appendix G. 10 This information is being updated as part of the LDW FS. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 121 Of particular importance to the cleanup and disposal of PCB contaminated waste at the T-117 EAA are the substantive requirements under TSCA (40 CFR 761.61) as an ARAR requirements under 40CFR761.61. Because of the complexity of the site, the removal of PCB contaminated soil and sediment is best suited for a risk-based disposal (40CFR761.61(c)), which is attained through application by providing the information outlined in 40CFR761.61(a)(3). The application informationprocess is intended to demonstrate that the removal action will not pose an unreasonable risk to human health or the environment. In order to meet this substantive requirement, tThis application will be prepared during the NTCRA design phase. Appendix H describes in further detail the information required to be provided for the risk-based disposal application. 4.3 REMOVAL ACTION LEVELS This section discusses the derivation of RvALs for the soil and sediment COCs identified in Section 3 and also considers practical quantitation limits (PQLs), background concentrations, and the total cancer risk per WAC 173-340-740(5)(a). The development of sediment RvALs is discussed in Section 4.3.1, Section 4.3.2 discusses the development of the soil RvALs, Section 4.3.3 discusses the development of groundwater RvALs, and Section 4.3.4 provides a summary of the selected RvALs for the T-117 EAA. The RvALs are used in Section 4.4 to develop the sediment and soil removal boundaries. A detailed discussion of the development of groundwater RvALs is presented in Appendix B. MTCA CULs are used as one basis for deriving RvALs, as MTCA is an ARAR for this site. Under MTCA, CULs for individual carcinogenic COCs for which other ARARs do not apply are typically calculated based on a risk level of 1 10-6. The total cancer risk allowed for multiple chemicals under MTCA is 1 10-5 (WAC 173-340-740(5)(a)). EPA's range is 10-4 to 10-6. Both MTCA and CERCLA equations and assumptions were used to calculate the total risks associated with the selected RvALs for soil. As noted above, the T-117 Sediment Study Area is located within the LDW and sediment remedial action levels have not been finalized under the LDW-wide CERCLA and MTCA remedial program. Consequently, T-117 sediment action levels cannot be set as final until the LDW ROD is completed. EPA has therefore specified that the T-117 NTCRA use a site-specific RvALs. Sediment RvALs for the T-117 Sediment Study Area are based on SMS (except for arsenic, cPAHs, and dioxins and furans which are discussed in more detail in Section 4.3.1 below). Similarly, EPA has also specified that the T-117 NTCRA use RvALs for soil in the Upland Study Area and the Adjacent Streets and Yards Study Area that have been developed based on the methodology set forth under MTCA for calculating soil CULs and defining appropriate points of compliance. Soil RvALs are thus protective of human health for exposure pathways present in the soil within the Adjacent Streets Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 122 and Residential Yards Study Areas. Soil RvALs must also be protective of sediment and aquatic life where excavation occurs and these soils are converted from uplands to intertidal sediment 4.3.1 Development of sediment removal action levels This section describes the development of sediment RvALs for the T-117 Sediment Study Area. As presented in Table 3-910, the COCs for the T-117 Sediment Study Area are PAHs, total PCBs, phenol, dioxins and furans, and arsenic. RvALs for phenol (0.42 mg/kg) and individual PAHs were set equal to the SQS, consistent with the corresponding lowest SLs used for these contaminants (Table 3-2). The SL for cPAHs was based on an EPA preliminary remediation goal (PRG) soil value protective of residential land use (0.015 mg/kg). cPAHs were also identified as a risk driver in the LDW HHRA (Windward 2007b) for seafood consumption and the direct sediment contact exposure pathways (i.e., beach play, netfishing, and clamming). Risk-based threshold concentrations (RBTCs) calculated from the LDW HHRA results were considered as RvALs for cPAHs because they are more relevant to exposure to sediment. The three RBTCs for cPAHs that were calculated in the LDW RI (Windward 2008), based on an assumed excess cancer risk of 1 10-6, were 0.09 mg/kg (for beach play), 0.15 mg/kg (for clamming), and 0.38 mg/kg (for netfishing). The lowest of these RBTCs (0.09 mg/kg) was selected as the RvAL for cPAHs in sediment at the T-117 EAA. An RBTC was not calculated for cPAHs for seafood consumption because most of the risk was associated with the consumption of clams from throughout the LDW, and the relationship between cPAHs in tissue and sediment was highly uncertain (Windward 2008). For total PCBs, RBTCs were calculated in the LDW RI (Windward 2008) for seafood consumption and the three direct sediment contact exposure scenarios. The RBTCs for the direct-contact scenarios were higher than the SL of 12 mg/kg OC (i.e., the SQS value); the RBTC for seafood consumption was lower than background concentrations (Windward 2008). Ultimately, total PCB sediment action levels for the LDW RI/FS may be influenced by background concentrations and other regulatory considerations. At the present time, EPA and Ecology have not made a final determination of action levels for the LDW project. Therefore, for the purposes of the T-117 EAA, the SQS (12 mg/kg OC ) was selected as the sediment RvAL for total PCBs. Because this RvAL is lower than all of the LDW RBTCs for the direct- contact scenarios, it is considered to be protective of human health under those scenarios. The RvAL is higher than the RBTC for seafood consumption, so it is not fully protective of human health for the seafood consumption pathway. Similarly, because the seafood consumption RBTC is below multiple potential background PCB concentrations and action levels will not be below background concentrations (WAC 173-340-700), the ultimate action level for the LDW project will be also be above the RBTC for seafood consumption. The removal of PCB-contaminated sediment, with concentrations above the SQS from within the Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 123 T-117 Sediment Study Area will reduce the site-wide PCB concentration and the risks associated with seafood consumption in the LDW. The SL for dioxins and furans was based on an EPA PRG for residential land use (4.5 ng/kg dioxin/furan TEQ). RBTCs were calculated in the LDW RI for the three direct sediment contact exposure scenarios. Although it was recognized that seafood consumption may also be an important exposure pathway for dioxins and furans, RBTCs were not derived for dioxins and furans because tissue data were not available at the time of the risk assessments (Windward 2008). The RBTCs for the three direct sediment contact exposure scenarios ranged from 13 to 37 ng/kg for a target risk of 1 10-6; these RBTCs were higher than the SL. Because the sediment RBTCs were based on sediment exposure scenarios, they are more relevant to the establishment of a sediment RvAL than the SL, which was derived for the direct contact residential soil exposure. Accordingly, the lowest of the three RBTCs (13 ng/kg, based on a tribal clamming scenario) was selected as the sediment RvAL for dioxins and furans. Ultimately, background concentrations of dioxins and furans may influence the derivation of an action level for the LDW RI/FS. Action levels determined for the LDW will be tracked to ensure the NTCRA is consistent with those of the LDW. The SL for arsenic was also based on an EPA PRG soil value for residential land use (0.39 mg/kg). Because arsenic was also a risk driver in the LDW HHRA, RBTCs were calculated in the LDW RI (Windward 2008) for the three direct sediment contact exposure scenarios discussed above.11 The RBTCs ranged from 1.3 to 3.7 mg/kg for a target risk of 1 10-6; these RBTCs were higher than the SL but were all lower than preliminary sediment background concentrations for arsenic that were reported in the LDW RI (Windward 2008). The action level for the LDW RI/FS have has yet to be determined, and but it will be influenced by background concentrations. The arsenic RvAL to be used for the T-117 Sediment Study Area will also be influenced by background sediment concentrations when such a determination iscan be made infor the LDW RI/FS. Therefore, an RvAL for arsenic of 12 mg/kg is assumed for the purposes of this EE/CA, which is similar to the background concentrations being considered for arsenic. This assumption will be reviewed during the design of the T-- 117 NTCRA. Risk estimates were made for the proposed sediment RvALs for the purposes of evaluating compliance with the MTCA requirements that cancer risks from individual contaminants not exceed 1 10-6 and that cumulative cancer total risks for all contaminants not exceed a excess cancer risk of 1 10-5 (Table 4-1). The cancer risk associated with the risk-based RvAL for each of the four carcinogenic COCs was at or 11 An RBTC was not calculated for arsenic for seafood consumption because most of the risk was associated with the consumption of clams from throughout the LDW, and the relationship between arsenic in tissue and sediment was highly uncertain (Windward 2008). Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 124 below the threshold of 1 10-6. A background-based RvAL was also developed for arsenic. The excess cancer risk for the background-based RvAL for arsenic was 4 10-6. TThe total cumulative risk from the carcinogenic COCs, regardless of whether the risk-based or background-based RvAL for arsenic was used, was well below the for the four carcinogenic COCs was 21 10-65, below the MTCA threshold. The sum of the HQs for the seven COCs with non-carcinogenic endpoints was 0.04, well below the MTCA threshold of 1. This evaluation indicates that the sediment RvALs are sufficiently protective. Table 4-1. T-117 Sediment Study Area total risks for sediment removal action levels under the recreational scenariosediment removal action levels RvAL (dwdry weight Source of Excess Hazard COC equivalent, mg/kg) RvAL Cancer Risk Quotient a Sediment Recreational Scenario b, c -67 Arsenic (risk-based) 2.812 LDW RI 15 10 na ba -6 Arsenic (background-based) 12 LDW RI 4 10 na b 2-Methylnaphthalene 0.59 SQS d na 0.0005 db Acenaphthene 0.25 SQS na 0.00007 db Anthracene 3.4 SQS na 0.00005 ec -6 cPAH TEQ 0.09 LDW RI 1 10 na db Dibenzofuran 0.23 SQS na na db Fluoranthene 2.5 SQS na 0.0003 db Fluorene 0.36 SQS na 0.00004 db Phenanthrene 1.6 SQS na na Phenol 0.42 SQS na 0.000004 dd 0.19 or bd -7 Total PCBs SQS 2 10 0.04 (12 mg/kg -OC) -5 ce -7 Dioxin/furan TEQ 1.3 10 0.000013 LDW RI 5 10 na -6 Total (risk-based) 3 10 0.04 -6 Total (background-based) 62 10 0.04 Note: a Recreational scenario equivalent to beach play scenario used in the LDW HHRA (Windward 2007b). ba The RBTCs for arsenic are less than preliminary background concentrations (Windward 2008). For the purposes of this evaluation, a value of (12 mg/kg) was used for the RvAL, which is similar to the background concentrations being considered in the LDW RI/FS for arsenic. b For the purposes of risk estimation, the SQS value originally given in units of mg/kg OC was converted to a dry weight concentration using the average TOC concentration in the T-117 Sediment Study Area (1.55%). ec Other PAHs identified as sediment COCs are not explicitly evaluated for human health risk, including the individual components of the cPAH TEQ sum [benzo(a)pyrene, benzo(b)fluoranthene, benzo(a)anthracene, benzo(k)fluoranthene, indeno(1,2,3-cd)pyrene, dibenz(a,h)anthracene, and chrysene]; benzo(g,h,i)perylene, for which human health toxicity benchmarks have not been established; and total LPAHs and HPAHs, which are not typically evaluated for human health risk. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 125 d If the SQS of 12 mg/kg OC is not used because the TOC in a sediment sample is either higher or lower than 0.5 to 3.5%, then a site-specific calculation, or "surrogate," can be applied, which results in a value of 0.19 mg/kg dw. ce This RvAL is derived from an RBTC (equivalent to 1 10-6) for tribal clamming. The excess cancer risk estimate given is for the beach play scenario, which has an RBTC approximately 2 times the RBTC for the tribal clamming scenario. d For the purposes of risk estimation, the SQS value originally given in units of mg/kg OC was converted to a dry weight concentration using the average TOC concentration in the T-117 Sediment Study Area (1.55%). If the SQS of 12 mg/kg OC is not used because the in a sediment sample is either higher or lower than 0.5 to 3.5%, then a site specific calculation, or "surrogate" can be applied which results in a value of 0.19 mg/kg dw. COC contaminant of concern PCB polychlorinated biphenyl cPAH carcinogenic polycyclic aromatic hydrocarbon RBTC risk-based threshold concentration dw dry weight RI remedial investigation FS feasibility study RvAL removal action level HHRA human health risk assessment SQS sediment quality standard HPAH high-molecular-weight polycyclic aromatic hydrocarbon T-117 Terminal 117 LDW Lower Duwamish Waterway TEQ toxic equivalent LPAH low-molecular-weight polycyclic aromatic hydrocarbon TOC total organic carbon OC organic carbonRvAL removal action level PCB polychlorinated biphenyl As mentioned previously, portions of the T-117 Upland Study Area may be converted in the future to aquatic habitat as part of the restoration and redevelopment plans for the T-117 EAA. As described further in Section 7, the sediment removal and/or capping actions would be sufficient to result in clean sediment or cap material extending to a minimum depth of up to 45 cm (Figure 4-1), which and would provide protection for clammers and children playing within the intertidal areas (i.e., between approximately +13.8 ft and 0 ft mean lower low water [MLLW]). Clams, which have a maximum burrowing depth of 35 cm (1.1 ft), and clammers, who may dig up as deep asto 45 cm (1.5 ft), and have direct-contact exposure would be protected. Figure 4-1 presents a conceptual diagram of the anticipated post-NTCRA conditions for both upland and aquatic areas. This latter depth would also be sufficient to accommodate a maximum erosion potential of 6 cm (2.5 in.) during a 100-yr storm event; monitoring to assess the stability of the cap may be a part of the sediment monitoring program. Additional information regarding LDW sediment dynamics within the T-117 Sediment Study Area is provided in Section 5. Because the final configuration of the sediment portion of the site is still being evaluated, a sediment cap design, if needed, would be based on US Army Corps of Engineers (USACE) guidance regarding the determination of cap thickness and the specific layers that are necessary for a cap that is dependent on the environment and the habitat in which it will be constructed. The cap design will be prepared during the NTCRA design phase and will take into account potential future habitat requirements. Section 6.1.2.2 presents additional details on the cap design. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 126 Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 127 Figure 4-1. Conceptual diagram of points of compliance for upland soil and sediment cleanup Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 128 4.3.2 Development of soil removal action levels This section describes the development of soil RvALs for the T-117 Upland Study Area and the Adjacent Streets and Residential Yards Study Area. As shown in Figure 4-2 and Table 4-2, the RvALs were calculated or developed using: MTCA Method B (Equations 740-1 and 740-2, WAC 173-340-740) ARARs CULs from MTCA based on potential exposure to applicable upland ecological receptors (TEE) (WAC 173-340-7490 through 7494) Potential influences on other media (e.g., the soil-to-groundwater [WAC 173-340-747] and groundwater-to-sediment pathways) were also considered. In addition, residual risks associated with COCs remaining at concentrations at or below the candidate RvALs were examined to determine if additional modifications were warranted or if adjustments were needed for COC-specific exposure scenarios (e.g., early life-stage exposure to cPAHs). The potential for the erosion of soil to sediment will be addressed as part of the NTCRA design. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 129 Figure 4-2. Development of soil removal action levels Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 130 Table 4-2. T-117 Upland Study Area soil removal action levels MTCA TPH Metals Regulation Heavy Oil-Range Dioxin/Furan Total a 173-340- Basis Unit Organics cPAH TEQ TEQ PCBs Arsenic Silver Potential CULs TSCA 740(3)(b)(i) mg/kg nc nc nc 1.0 nc nc 40 CFR 761.61(4)(i)(A) TEE mammalian mg/kg 6,000 11.75 nc 0.65 7.1 nc predator (shrew) TEE, avian predator mg/kg 6,000 nc nc 3.5 150.3 nc 740(3)b)(ii) (robin) TEE, mammalian mg/kg 6,000 82.35 nc 14.4 42.9 nc herbivore (vole) -6 TEE, plants/soil biota mg/kg 200 nc 2 10 40 10 2.0 direct contact, non- 740(3)b)(iii)(B)(I) mg/kg nc nc nc nc 24 400 carcinogen direct contact, -5 mg/kg nc 0.14 1.1 10 0.50 0.67 nc carcinogen 740(3)b)(iii)(B)II) preliminary human -5 b mg/kg 2,000 0.14 1.1 10 1.0 0.67 400 health CUL c d -10 e PQLs mg/kg 25/100 0.008 1.5 10 0.01 0.1 0.02 700(6)(d) f background mg/kg na na na na 7.3 na Summary of Applicable CULs Used as a Basis for RvALs TEE wildlife/plants/soil -5 h 1.1 10 2 biota, human health mg/kg 200 0.140.008 -6 0.65 7.3 2.0 g 10 direct contact (< 2 ft) TEE plants/soil biota, 740 h -5 human health direct mg/kg 200 0.140.008 1.1 10 1.0 7.3 2.0 g contact (2 to 6 ft) all other soil ( 6 to15 ft -5 mg/kg 2,000 0.14 1.1 10 1.0 7.3 400 below grade) a NWTPH-Dx (diesel and lube oil ranges). Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 131 b -6 Total cancer risk for all human health CULs is 5 10 ; total hazard index is 1. c 25 mg/kg is the diesel-range PQL; 100 mg/kg is the heavy oil-range PQL. d PQL is based on site-specific PQLs for benzo(a)pyrene. e PQL assumes a single Aroclor (1260) for PCBs. f Background soil concentrations based on Puget Sound average from Natural Background Soils Metals Concentrations in Washington State Toxics Cleanup Program (Ecology 1994c). g Soil CULs (used as a basis for selecting RvALs) for TPH, dioxins and furans, copper, and silver based on protection of plants or soil biota per the TEE requirements are subject to change based on further site-specific TEE evaluation. h cPAH TEQ is adjusted for combined early life stage adjustments and soil exposure factors for residential and recreational PRG (Appendix I). ARAR Applicable or Relevant and Appropriate nc no criteria TEE terrestrial ecological evaluation Requirement nd nc not datacalculated TEQ toxic equivalent BCF bioconcentration factor NWTPH Northwest total petroleum hydrocarbons TPH total petroleum hydrocarbons cPAH carcinogenic polycyclic aromatic PCB polychlorinated biphenyl TPH-Dx total petroleum hydrocarbons hydrocarbon PQL practical quantitation limit diesel and oil extractable CPF carcinogenic potency factor RfD reference dose TSCA Toxic Substances Control Act CUL cleanup level RvAL removal action level WAC Washington Administrative Code CWA Clean Water Act T-117 Terminal 117 na not availableapplicable Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 132 4.3.2.1 T-117 Upland Study Area As presented in Table 3-110, the soil COCs for the T-117 Upland Study Area are total PCBs, TPH, cPAHs, dioxins and furans, silver, and arsenic. Table 4-2 lists the MTCA regulations that were used to determine the T-117 Upland Study Area soil RvALs for the identified COCs. The derivation of the RvALs for each COC is described below. Total PCBs An RvAL of 1.0 mg/kg was selected for total PCBs for most of the T-117 Upland Study Area based on the TSCA ARAR. According to MTCA, if it can be demonstrated that an ARAR is sufficiently protective, the ARAR may be used to establish a CUL under MTCA (WAC 173-340-740(3)(b)(iii)). An ARAR is considered sufficiently protective if it is associated with a cancer risk of 1 10-5 or less (WAC 173-340-740(5)(b)). The TSCA CUL of 1.0 mg/kg, proposed for use as an RvAL for the T-117 NTCRA, equates to an excess cancer risk12 of 2 10-6. A different RvAL is applicable to areas within the T-117 Upland Study Area that may become upland habitat. For those areas, the RvAL is based on the MTCA-defined soil CUL for total PCBs of 0.65 mg/kg, which is relevant within limited soil depths based on a TEE for terrestrial receptor exposure (Table 4-2). The development of a TEE-based RvAL is appropriate inasmuch as the eventual size of the landscaped upland portion of a future T-117 habitat area may exceed the MTCA-defined 0.25-acre threshold for a TEE exclusion. Under the habitat restoration scenario, the T-117 Upland Study Area would be required to undergo a site-specific TEE rather than a simplified TEE. The most stringent default TEE CUL under MTCA is based on the protection of the mammalian predator (shrew) and is also protective of plants (the MTCA TEE CULs for the soil biota, avian predator, and mammalian herbivore are significantly greater and would not be a limiting factor). Burrowing mammalian predators, such as the shrew, and their primary food source of worms and insects are found in the top 1 to 2 ft of soil (Suter 1993). As a result, a conditional point of compliance of the upper 2 ft for the soil RvAL based on the MTCA TEE CUL is proposed, consistent with WAC 173-340-7490(4)(a). Plant roots would penetrate the full depth of the biologically active zone defined as the upper 6 ft in MTCA. Institutional controls, such as a property usedeed restrictions and a monitoring and maintenance plan, would be implemented at the developed habitat site to ensure that any disturbance of soil would be managed to protect ecological receptors. Institutional controls would also include the written notification of workers regarding maintenance-related limitations and signs stating the prohibition of unplanned digging within any habitat areas. To address any potential concerns regarding exposure through the consumption of home-grown produce, the risk level associated with the PCB RvAL of 1.0 mg/kg was 12 Calculated using MTCA Equation 740-2 and a carcinogenic potency factor of 2 per mg/kg-day. Lower Duwamish Waterway Superfund Site: Draft Final EE/CA T-117 Early Action Area June 3, 2010 Page 133 compared to risks associated with this pathway to determine if adjustment was needed. Based on a review of the literature, including a risk assessment conducted by the US Army Corps of Engineers (USACE) and EPA (Weston Solutions 2005) for the Housatonic River,13 exposures associated with the consumption of produce grown in soils that contain total PCBs and dioxins and furans at the T-117 RvALs would not increase the total risk to a level in excess of 1 x 10-5. Though not reported in the referenced risk assessment, the risk corresponding to an exposure level of 1.0 mg/kg would be 1.5 10-6, which is less than the risk of 2 10-6 posed by the ARAR based TSCA soil RvAL of 1.0 mg/kg. TPH To accommodate possible future use of the T-117 Upland Study Area for habitat, an RvAL of 200 mg/kg was selected for the upper 6 ft of soil. For depths below 6 ft, an RvAL of 2,000 mg/kg was selected for TPH based on MTCA Method A CULs (Table 4-2). The Method A CUL is based on preventing the accumulation of diesel- range TPH in groundwater in a coarse sand and gravel matrix and is lower than health- based TPH criteria for diesel. A TPH fraction analysis was not performed at T-117 to calculate a human health risk-based TPH value. cPAH TEQ Per EPA (2005e) guidance, the evaluation of early life-stage exposure to cPAHs was considered in the development of the RvAL for cPAHs because of the potential for the future exposure of children in areas of the T-117 Upland Study Area that may be made available for public access. cPAHs are the only COCs considered to be mutagenic, so they are the only COCs for which this adjustment may be necessary. The adjusted RvAL was less than the PQL, thus an RvAL of 0.008 mg/kg TEQ was selected for cPAHs based on PQLs for individual PAHs. Nevertheless, the adjusted RvAL was Early lifestage exposure parameters were used in the calculations of total risk to evaluate protectiveness under CERCLA for the recreational exposure scenario (Table 4-3). Additional details of this adjustment to account for early life-stage exposure are provided in Appendix I. The cPAH RvAL of 0.14 mg/kg TEQ was selected based on the MTCA Method B ARAR. 13 The risk assessment estimated that the reasonable maximum exposure cancer risk associated with the consumption of produce grown in garden soil containing total PCBs at 2 mg/kg was 3 10-6. The assessment used consumption rates for home-grown foods in three categories: exposed vegetables (11 kg/yr), root vegetables (10 kg/yr), and exposed fruit (12 kg/yr). Lower Duwamish Waterway Superfund Site: Draft Final EE/CA T-117 Early Action Area June 3, 2010 Page 134 Table 4-3. T-117 Upland Study Area total risks for soil removal action levels Excess Cancer Risk at RvAL MTCA Unrestricted Land Use CERCLA MTCA MTCA Unrestricted Unrestricted Land Use Land Use CERCLA CERCLA Total Incremental Industrial Recreational RvAL Source of Risk(unitless Risk(unitless) Scenario Scenario a b b, cd (unitless)cd cd, e, f COC (mg/kg) RvAL ) (unitless) d -56 -7 2.6 x 10-602 Arsenic 0.677.3 MTCA Method B 1 10 0 04 10 -7 10 -8 -78 Silver 2400 MTCA Method B nNc nc 837 10 2 10 -6 -6 -7 -6 cPAH TEQ 0.14 MTCA Method B 1 6 10 16 10 6 10 6 10 -6 -6 -6 -7 Total PCBs 1.0 Method B/TSCA 2 10 2 10 1 10 6 10 Dioxin/furan -5 -6 -6 -7 -7 1.1 10 MTCA Method B 1 10 1 10 6 10 3 10 TEQ -56 -6 -6 -6 Total 1.52 10 49 10 23 10 7 10 a For total PCBs, the RvAL was based on the TSCA ARAR using MTCA Method B CUL development procedures. For other COCs, the MTCA Method B standard equation value was used. b Risk was calculated according to the standard MTCA Method B equation and assumptions with adjustments to the cPAH risk based on early life-stage exposure parameters (Appendix I). dc The arsenic RvAL is based on natural background. The MTCA risk calculation was performed both using the natural background risk associated with arsenic and the incremental risk of the arsenic RvAL relative to natural background (which is zero). The second risk calculation demonstrates compliance with the MTCA total risk -5 threshold of 1x10 (WAC 173-340-740(5)(a)).and corresponding risk used to calculate total risks is the MTCA Method B value, which is lower than the selected RvAL of 7.3 mg/kg, which is based on the soil background concentration. c Risk was calculated according to CERCLA equations and assumptions appropriate to the scenario. e The exposure frequency for the recreational scenario was 48 days/yr. f The CERCLA recreational scenario risk calculation incorporates early life stage adjustments (Appendix I). CERCLA Comprehensive Environmental Response, Compensation, PCB polychlorinated biphenyl and Liability Act RvAL removal action level COC contaminant of concern T-117 Terminal 117 cPAH carcinogenic polycyclic aromatic hydrocarbon TSCA Toxic Substances Control Act MTCA Model Toxics Control Act nc non-carcinogens (not included in the MTCA total cancer risk analysis) Ecology is currently evaluating early life-stage exposure and is considering rule revisions to address this issue. On March 22, 2010, Ecology released a document with examples of updates to MTCA specifically related to cPAHs and early -life-stage exposure (Appendix I). The information and examples are currently under discussion among the MTCA /SMS Advisory Group members. Although early life-stage exposures are not currently incorporated into MTCA, the total risk calculation in Table 4-3 for the MTCA unrestricted-land-use scenario incorporates early life-stage exposure assumptions. Additional details on the adjustment to account for early life-stage exposures are provided in Appendix I. The cPAH soil RvAL may be below natural or anthropogenic background concentrations. Background concentrations have not been Lower Duwamish Waterway Superfund Site: Draft Final EE/CA T-117 Early Action Area June 3, 2010 Page 135 evaluated in this EE/CA but may be evaluated during remedial design. Ecology's document provided a mean background cPAH concentration of 1.8 mg/kg. Dioxin/Furan TEQ The RvAL of 11 ng/kg TEQ for dioxin/furan was selected for the T-117 Upland Study Area. This RvAL is equal to the MTCA Method B risk-based concentration that corresponds to a carcinogenic risk of 1 x 10-6. A recurring issue in risk assessment is the calculation of acceptable or safe levels of dioxins and furans in soil. EPA is currently undertaking a comprehensive review of this issue as part of its "dioxin reassessment." This work includes an examination of dioxin and furan soil action levels in use across the United States and internationally. On January 7, 2010, EPA's Office of Solid Waste and Emergency Response (OSWER) issued draft recommended interim PRGs for dioxin and furan soil at CERCLA and RCRA sites (EPA 2009b). The proposed draft recommended interim PRGs are 72 ng/kg TEQ for residential land uses and 950 ng/kg TEQ for commercial/industrial land uses. These draft recommended interim PRGs are lower than the previous value of 1,000 ng/kg TEQ for dioxin in residential soil and lower than the range of 5,000 to 20,000 ng/kg TEQ for dioxin in commercial/industrial soil. EPA expects to issue a final interim PRG by June 2010. Currently, several soil criteria are being used by different government organizations, as listed below. These criteria are presented for informational uses only; none of these criteria are applicable under MTCA (i.e., they are not ARARs). EPA current residential soil cleanup standard: 1,000 ng/kg TEQ (EPA 1998). This standard forms the basis of the 1998 PRG and is the starting point for the derivation of CULs at CERCLA and RCRA sites. This value reflects an excess cancer risk of approximately 2.5 10-4 based on exposure and toxicity parameters used in 1998. This PRG is being reassessed as noted above, and may be lowered to 72 ng/kg TEQ. This draft PRG corresponds to an excess cancer risk of 1 10-5. The EPA 2009 residential PRG (for Regions 3, 6, and 9) used for screening: 4.5 ng/kg TEQ (EPA 2009e). This PRG is based on an excess cancer risk of 1 10--6 and uses somewhat different exposure and toxicity parameters than those used in 1998 (listed above). This concentration is used for screening at CERCLA sites and is not necessarily used as a CUL. Agency for Toxic Substances and Disease Registry (ATSDR) direct-contact residential exposure SL is 50 ng/kg TEQ (73 FR 61133). This value is not a threshold for toxicity but is used as a SL by ATSDR health assessors to determine when to conduct health evaluations (i.e., when dioxins and furans are present above this level). Washington State Department of Health (WSDOH) site-specific health assessment: levels that trigger health assessment by WSDOH are site-specific. Lower Duwamish Waterway Superfund Site: Draft Final EE/CA T-117 Early Action Area June 3, 2010 Page 136 Silver To accommodate possible future use of the T-117 Upland Study Area for habitat, an RvAL of 2.0 mg/kg was selected for the upper 6 ft of soil based on the MTCA TEE. For depths below 6 ft, an RvAL of 400 mg/kg was selected for silver based on MTCA Method B (Table 4-2). The higher concentration was evaluated in conjunction with those of other non-carcinogenic COCs to ensure that the total hazard index for the site was less than 1.0. Arsenic A preliminary RvAL of 0.67 mg/kg was calculated for arsenic based on human health considerations. However, because this concentration was less than the preliminary natural background concentration in the Puget Sound region (7.3 mg/kg) (Ecology 1994c), an RvAL of 7.3 mg/kg was selected. This RvAL does not result in a total hazard index of greater than 1.0 when considered together with contributions from other noncarcinogenic COCs. Assessment of Total Risk The total excess cancer risk associated with each for the selected RvALs was assessed for the MTCA unrestricted- land- use scenario and for recreational and industrial scenarios under CERCLA. The MTCA unrestricted land use and CERCLA recreational scenarios incorporated early life-stage exposure parameters risk calculations and RvALs based on MTCA-derived CULs, described above for individual contaminants, were assessed for total risk for both recreation and commercial exposure scenarios to ensure compliance. Detailed back-up for these risk calculations is presented in Appendix I. The total risks for the recreational and coindustrialmmercial land use scenarios (under CERCLA) were 7 6 10-6 and 3 2 10-6, respectively (Table 4-3), which were within the acceptable CERCLA 10-4 to 10-6 risk range. The total risks for the recreational and commercial land use scenarios (under MTCA unrestricted land use scenario) wasere each 1.552 10-56 (Table 4-3). When the incremental arsenic risk was adjusted relative to natural background, the risk was reduced to 49 10-6, ; risks estimates for both scenarios were less than the 10-5 MTCA threshold. 4.3.2.2 Adjacent Streets and Residential Yards Study Area As presented in Table 3-110, the soil COCs for the Adjacent Streets and Residential Yards Study Area are total PCBs and dioxins and furans. An RvAL of 1 mg/kg was selected for total PCBs based on the TSCA ARAR, and an RvAL for dioxin/furan TEQ of 11 ng/kg was selected based on MTCA Method B. Utility workers and residents may be exposed to soils within the Adjacent Streets and Residential Yards Study Area. MTCA does not have a CUL for utility workers, so the residential scenario was used to evaluate exposures under MTCA for both areas. CERCLA does have a utility worker scenario; risks were calculated for the worker Lower Duwamish Waterway Superfund Site: Draft Final EE/CA T-117 Early Action Area June 3, 2010 Page 137 scenario.14 As shown in Table 4-4, these total risk estimates were less than 10-5 (MTCA) and were within the CERCLA range of 10-4 to 10-6. Table 4-4. T-117 Adjacent Streets and Residential Yards Study Area total risks for soil removal action levels Excess Cancer Risk at RvAL CERCLA MTCA CERCLA Utility CERCLA Residential CERCLA Unrestricted Worker Scenario Scenario for Adjacent Recreational RvAL Source of Land Use for Adjacent Streets and Residential Scenario a b b c, d,. e COC (mg/kg) RvAL (unitless) Streets (unitless) Yards (unitless) (unitless) Adjacent Streets Utility Worker Scenario -6 -8 -6 -6 Total PCBs 1.0 TSCA 2 10 2 10 5 10 4.5 10 -5 -6 -8 -6 -6 Dioxin/furan TEQ 1.1 10 Method B 1 10 1 10 2 10 2.4 10 -6 -8 -6 -6 Total 3 10 3 10 7 10 6.9 10 a Risk was calculated according to the standard MTCA Method B equation and assumptions. b Risk was calculated according to CERCLA equations and assumptions appropriate to the scenario. For the residential scenario, these are standard default assumptions used by EPA Regions 3, 6, and 9. c Risk was calculated according to CERCLA equations and assumptions appropriate to the scenario. d The exposure frequency for the recreational scenario was 48 days/yr. e The CERCLA recreational scenario risk calculation incorporates early life- stage adjustments (Appendix I). CERCLA Comprehensive Environmental Response, PCB polychlorinated biphenyl Compensation, and Liability Act RvAL removal action level EPA US Environmental Protection Agency TEQ toxic equivalent MTCA Model Toxics Control Act 4.3.3 Development of groundwater removal action levels This section describes the development of groundwater RvALs for the T-117 Upland Study Area and the Adjacent Streets. As shown in Figure 4-3 and Table 4-5, the RvALs were calculated or developed using: MTCA Method B (Equations 7240-1 and 7240-2, WAC 173-340-7240) ARARs ( Ssurface water protection criteria using MTCA Equation 730-2 with a site-specific fish consumption rate of 57 g/day and a fish diet fraction of 1 for the Duwamish 14 Risks for the utility worker scenario were calculated using the following equation: risk = 1 x 10-6 x MTCA CUL/utility worker PRG, where risk is unitless and the MTCA CUL and the utility worker PRG are both expressed as mg/kg. The utility worker PRGs for PCBs and dioxins and furans were derived by adjusting the industrial PRGs as follows: the exposure frequency was adjusted down from 250 days/yr to 30 days/yr; the exposure duration was adjusted down from 25 yr to 1 yr; and the soil ingestion rate was adjusted up from 100 mg/day to 330 mg/day. Lower Duwamish Waterway Superfund Site: Draft Final EE/CA T-117 Early Action Area June 3, 2010 Page 138 corridor and Elliott Bay based on the King County Asian Pacific Islander seafood consumption survey) (EPA 1999) CULs from MTCA based on background concentrations (e.g., Method A for arsenic) CULs from based on site site-specific background concentrations Lower Duwamish Waterway Superfund Site: Draft Final EE/CA T-117 Early Action Area June 3, 2010 Page 139 Figure 4-3. Development of groundwater cleanup levels Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 140 Table 4-5. T-117 Upland Study Area groundwater removal action levels TPH (Heavy Oil MTCA Regulation -Range Total Total a (WAC 173-340)- Basis Unit Organics) cPAH TEQ BEHP PCBs Silver Arsenic Total Risk Surface Water b 730(3)(b)(i)(A) WAC 173-201A, marine g/L nc nc nc 3.00E-02 1.9 36 c 730(3)(b)(i)(B) Sec. 304, CWA, marine, chronic g/L nc nc nc 3.00E-02 1.9 36 c 730(3)(b)(i)(B) Sec. 304, CWA, organism only g/L nc 1.80E-02 2.2 0.000064 nc 0.14 40CFR131, NTR, marine, 730(3)(b)(i)(C) d g/L nc nc nc 0.03 1.9 36 chronic 40CFR131, NTR, organism 730(3)(b)(i)(C) d g/L nc 3.10E-02 5.9 0.00017 nc 0.14 only environmental effects g/L nc nc nc nc nc nc appropriate ARAR g/L nc 0.0180 2.2 0.000064 1.9 5 CPF (kg-day/mg) na 7.3 0.014 2 na 1.5 oral RfD (mg/kg-day) na na 0.02 na 0.005 0.0003 730(3)(b)(ii) BCF na 30 130 31000 0.5 44 6.01.38E- 1.3E- 066.12E- 1.43E1E- cancer risk na na 1.1E-04 076 66.18E-07 071.3E-6 0604 0.0120.005 1.5E- 0.5970.007 hazard quotient na na na 0.609 5157 047.3E-05 92 human health, fish consumption, 730(3)(b)(iii)(A) g/L nc nc 399 nc 25,926 17.7 non-carcinogen human health, fish consumption, 0.00010000 730(3)(b)(iii)(B) g/L nc 0.0296014 3.61.7 nc 0.0982047 carcinogen 5 Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 141 TPH (Heavy Oil MTCA Regulation -Range Total Total a (WAC 173-340)- Basis Unit Organics) cPAH TEQ BEHP PCBs Silver Arsenic Total Risk human health, fish consumption, g/L 500 na na na na na petroleum mixture 0.00006400 preliminary CUL g/L 500 0.0180014 2.21.7 1.9 0.0982047 005 730(3)(b)(iii)(C) 6.11.0E- 1.0E- 1.0E- 1.0E- 4.0E- cancer risk na na 0706 066.2E-07 066.1E-07 061.43E-06 063.3E-06 7.33E- hazard quotient na na 0.006009 na 0.008006 0.015 050.0002 e PQLs g/L 250/500 0.15 1.0 0.01 0.02 0.02 700(6)(d) 0.00022ntc 1.37not 0.00033not nanot 0.71not f background g/L not calculatedn calculatedn calculatedn calculatedn calculated tc tc tc tc 730 CUL g/L 500 0.15 2.21.7 0.01 1.9 0.710.05 Groundwater MCL, SDWA g/L nc nc 6.0 0.5 nc 10 MCLG for non-carcinogens, 720(4)(b)(i) g/L nc nc nc nc 100 10 SDWA MCL, WSDOH g/L nc nc nc nc nc nc protect surface water (from 0.00006400 g/L 500 0.0180014 2.21.7 1.9 0.7105 above) 005 0.00006400 preliminary CUL g/L 500 0.018014 2.21.7 1.9 0.09805 005 720(4)(b)(ii) 6.11.0E- 1.0E- 6.11.0E- cancer risk na na 1.4E0E-06 3.34.0E-06 0706 066.2E-07 0706 7.3E- hazard quotient na na 0.006009 na 0.0068 0.014015 050.00002 e g PQLs g/L 250/500 0.15 1.0 0.01 0.02 0.5 700(6)(d) h background g/L na na na na na 5 Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 142 TPH (Heavy Oil MTCA Regulation -Range Total Total a (WAC 173-340)- Basis Unit Organics) cPAH TEQ BEHP PCBs Silver Arsenic Total Risk 720 CUL g/L 500 0.15 2.21.7 0.01 1.9 5 720(8)(e) shoreline compliance level 12,500 0.15 5542.5 0.01 47.5 17.85 a NWTPH-Dx (diesel- plus lube oil-ranges). b Table 240(3) WAC 173-201A. c National recommended water quality criteria (EPA 2002). d 40CFR131.35, revised July 1, 2003. e PQL assumes a single Aroclor (1260) for PCBs and incorporates the TEF calculation for cPAH. f Background surface water concentrations are based on water quality upgradient of the LDW as indicated in the draft feasibility study (ENSR|AECOM 2009). g 250 g/L is the diesel-range PQL; 500 g/L is the lube oil-range PQL. h Background groundwater concentration for arsenic is based on MTCA Method A, and concentration for copper is based on site-specific statistical data analysis. . i CULs are MTCA-defined CULs. These serve as a basis for the RvALs throughout the EE/CA. Human health surface water quality criteria based on bioaccumulation have been conservatively assumed to apply to groundwater discharges even though the applicability of these criteria is uncertain. I Equation 730-2 in MTCA was modified to include the site-specific Asian Pacific Islander fish consumption rate of 57 g/day and fish diet fraction of 1 for the Duwamish corridor and Elliott Bay. The EPA consumption rate for the LDW of 97 g/day is not appropriate for the computation of MTCA surface water CULs. ARAR applicable or relevant and appropriate requirement EPA US Environmental Protection Agency PCB polychlorinated biphenyl BCF bioconcentration factor LDW Lower Duwamish Waterway PQL practical quantitation limit BEHP bis(2-ethylhexyl) phthalate MCL maximum contaminant level RfD reference dose CFR Code of Federal Regulations MCLG maximum contaminant level goal RvAL removal action levels cPAH carcinogenic polycyclic aromatic hydrocarbon MTCA Model Toxics Control Act SDWA Safe Drinking Water Act CPF carcinogenic potency factor na not applicable TEF toxic equivalency factor CUL cleanup level nc no criteria TPH total petroleum hydrocarbons CWA Clean Water Act NTR National Toxics Rule WAC Washington Administrative Code EE/CA engineering evaluation/cost analysis NWTPH-Dx Northwest total petroleum hydrocarbons diesel and WSDOH Washington State Department of EPA US Environmental Protection Agency lube oil Health Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 143 Because groundwater in the vicinity of the T-117 Upland Study Area is not potable, as described in Appendix B, MTCA cancer risks for groundwater ingestion were not calculated. The total cancer risk was calculated (Table 3-B-348) based on surface water protection using MTCA Equation 730-2, as modified. The total cancer risk for groundwater protective of surface water was less than 44.0 10-6, below the acceptable total risk range threshold of 10-5. The HQ, calculated using MTCA Equation 730-1, was 0.015, well below the acceptable total HQ of 1. CERCLA risks were not calculated for groundwater, inasmuch as it is not suitable for domestic use. As presented in Table 3-98, the groundwater COCs for the T-117 Upland Study Area include arsenic, copper, silver, PCBs, TPH, cPAH TEQ, and BEHP. Table 4-5 lists the regulations that were used to determine the T-117 Upland Study Area groundwater RvALs for the identified COCs. The derivation of the RvALs for each COC is summarized below. and described in detail in Appendix B. Arsenic Arsenic background values were determined based on MTCA Method A. A site-specific background value was not calculated because of the small sample set and elevated reporting limits. Reporting limits for select sampling events were significantly greater than the MTCA Method A value. The arsenic RvAL was 5 g/L. Silver and BEHP Silver and BEHP RvALs are based on the protection of surface water. RvALs were derived from published standards defined in the Clean Water Act. The silver RvAL is 1.9 g/L, and the BEHP RvAL is 2.21.7 g/L. TPH The TPH RvAL is based on the MTCA Method A value because no surface water quality criterion is available. The TPH RvAL is 500 g/L. Total PCBs and cPAH TEQ The total PCBs and cPAH TEQ RvALs are based on practical qualitative limits, which represent the practical level that analytical laboratories can sample and report results. The RvAL for total PCBs is 0.01 g/L, and the RvAL for cPAH TEQ is 0.15 g/L. 4.3.4 Summary of T-117 EAA removal action levels Sediment, soil, and groundwater RvALs derived in Section 4 for T-117 EAA COCs are summarized in Table 4-6. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 144 Table 4-6. T-117 EAA sediment, and soil, and groundwater removal action levels a b Sediment Soil Groundwater T-117 Sediment T-117 Upland Adjacent Residential T-117 Upland ic COCs Study Area Study Area Streets Yards Study Area Metals cd Arsenic 12 mg/kg 7.3 mg/kg na na 5 g/L Copper na na na na 3.4 g/L de Silver na 2.0/400 mg/kg na na 1.9 g/L PAHs ef 2-Methylnaphthalene 0.59 mg/kg na na na na ef Acenaphthene 0.25 mg/kg na na na na ef Anthracene 3.4 mg/kg na na na na ef Benzo(a)anthracene 1.7 mg/kg na na na na ef Benzo(a)pyrene 1.5 mg/kg na na na na ef Benzo(g,h,i)perylene 0.48 mg/kg na na na na Total ef 3.6 mg/kg na na na na benzofluoranthenes fg fg cPAH TEQ 0.09 mg/kg 0.00814 mg/kg na na 0.15 g/L ef Chrysene 1.7 mg/kg na na na na ef Dibenzo(a,h)anthracene 0.19 mg/kg na na na na ef Dibenzofuran 0.23 mg/kg na na na na ef Fluoranthene 2.5 mg/kg na na na na ef Fluorene 0.36 mg/kg na na na na ef Indeno(1,2,3-cd)pyrene 0.53 mg/kg na na na na ef Phenanthrene 1.6 mg/kg na na na na ef Total HPAH (calc'd) 15 mg/kg na na na na ef Total LPAH (calc'd) 5.7 mg/kg na na na na TPH Diesel- and lube oil- 200/2,000 na gh na na 500 g/L range hydrocarbons mg/kg Other SVOCs BEHP na nc na na 2.21.7 g/L Phenol 0.420 mg/kg na na na na PCBs ef, Total PCBs 0.19 mg/kg dw hj 0.65/1.0 mg/kg 1.0 mg/kg 1.0 mg/kg 0.01 g/L ij or 12 mg/kg - Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 145 a b Sediment Soil Groundwater T-117 Sediment T-117 Upland Adjacent Residential T-117 Upland ic COCs Study Area Study Area Streets Yards Study Area OC Dioxins and Furans Dioxin/furan TEQ 13 ng/kg 11 ng/kg 11 ng/kg 11 ng/kg na a Sediment point of compliance for the intertidal area is the top 10 cm for protection of benthic organisms and human health; the subtidal point of compliance is the top 45 cm for protection of human health. b Upland soil point of compliance is the depth at which the RvAL is reached, not to exceed 15 ft. jc If the SQS value of 12 mg/kg OC is not used because the TOC in a sediment sample is either higher or lower than 0.5 to 3.5%, then a site-specific calculation, or "surrogate," can be applied, which results in a value of 0.19 mg/kg dw. cd This RvAL is lower than preliminary background concentration (Windward 2008) and has been adjusted upward. The background concentration forlowest LDW RBTC for arsenic is 1.3 mg/kg; however, the RvAL is 12 mg/kg, which is similar to background concentrations being considered for arsenic. d e The TEE-based RvAL is 2.0 mg/kg in the upper 02 to 6 ft of soil for areas to be protective for terrestrial ecological exposures defined under MTCA and as determined by the type of biota to be present. The RvAL is 400 mg/kg for soils deeper than 6 ft. e f These RvALs were established based on SQS values, which were originally presented in units of mg/kg OC. The OC-normalized units were converted to mg/kg dry weight using a TOC concentration of 1.55%, reflecting the average TOC concentration in the T-117 Sediment Study Area based on both surface and subsurface sample results. For PCBs, If the SQS value of 12 mg/kg OC is not used because the TOC value in a sediment sample is either higher or lower than 0.5 to 3.5%, then a site-specific calculation, or "surrogate," can be applied, which results in a value of 0.19 mg/kg dw. f g These RvALs are likely to be lower than applicable background concentrations and may need to be adjusted upward. g h TEE-based RvAL is 200 mg/kg in the upper 02 to 6 ft of soil for areas to be protective for terrestrial ecological exposures defined under MTCA and as determined by the type of biota to be present. The RvAL is 2,000 mg/kg for soils deeper than 6 ft. h i TEE-based RvAL is 0.65 mg/kg in the upper 2 ft of soil for areas to be protective for terrestrial ecological exposures defined under MTCA. The RvAL is 1.0 mg/kg for soils deeper than 2 ft. i j The point of compliance for the groundwater RvALs is the point of exposure or the location where groundwater discharges to surface water (see Figure 4-1). BEHP bis(2-ethylhexyl) phthalate nc no criteria cPAH carcinogenic polycyclic aromatic hydrocarbon OC organic carbon COC contaminant of concern PAH polycyclic aromatic hydrocarbon dw dry weight PCB polychlorinated biphenyl HPAH high-molecular-weight polycyclic aromatic RBTC risk-based threshold concentration hydrocarbon RvAL removal action level LDW Lower Duwamish Waterway SQS sediment quality standards LPAH low-molecular-weight polycyclic aromatic SVOC semivolatile organic compound hydrocarbon TEE terrestrial ecological evaluation MTCA Model Toxics Control Act TEQ - toxic equivalent na not applicable TOC total organic carbon nc no criteria TPH total petroleum hydrocarbons Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 146 4.4 REMOVAL BOUNDARY DETERMINATION This section discusses the process for identifying the removal boundaries for each of the T-117 EAA study areas and presents the boundaries. Removal boundaries were determined based on RvALs for the identified T-117 COCs. The lateral extent of the removal boundary boundaries for each portion of T-117 EAA study areas is presented on Map 4-1. The area within the removal boundary is referred to as the removal area. 4.4.1 T-117 Sediment Study Area A sediment removal boundary was developed in the 2005 EE/CA (Windward et al. 2005c) using a weight-of-evidence approach that included a comparison of site sediment chemistry data to SMS and consideration of COCs identified in the LDW HHRA (Windward 2007b) and ERA (Windward 2007a). Since that time, RBTCs were developed and preliminary background data were compiled for the LDW RI (Windward 2008). Although the LDW RI does not specify sediment action levels, a preliminary comparison presented in the RI showed that many of the RBTCs were less than background concentrations. EPA's stated intention for the T-117 EAA is to sufficiently clean up the EAA so that future T-117 cleanup actions are not necessary under the LDW Record of Decision (ROD) (EPA 2007b). EPA therefore is requiring that the T-117 sediment cleanup boundary be based on a point-by-point RvAL rather than based on the previously approved weight-of-evidence approach that was used to derive the 2005 sediment removal boundary. The sediment removal boundary shown on Map 4-1 has been delineated to encompass all sampling locations with PCB concentrations greater than the RvAL. Total PCBs was the most prevalent COC, and the PCB RvAL is primarily responsible for determining the delineation of the removal boundary. All other COCs with concentrations greater than their RvALs are also contained within the removal boundary. As discussed in Section 4.3.1, the depth of compliance is 45 cm. 4.4.2 T-117 Upland Study Area The removal boundary for the T-117 Upland Study Area is presented on Map 4-1 and is discussed relative to each applicable upland COC in this section. PCBs, dioxins and furans, cPAH, arsenic and TPH were identified as COCs for the T-117 Upland Study Area. This boundary encompasses all of the areas where soil will be removed to meet the RvALs for the COCs both spatially and by depth (i.e., up to 15 ft deep) to allow for the broadest possible range of land uses in the future. As required per SOW Amendment 1, a spatial analysis of the distribution of PCB and TPH concentrations (Maps 4-2 through Map 4-7) was used to verify that the proposed removal prisms (i.e., the three-dimensional removal boundaries) will be located and sized to ensure the removal of all soil that exceeds the RvAL. These maps were created Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 147 using statistical interpolation to estimate PCB and TPH concentrations at locations other than those that were actually sampled, and thus introduce some uncertainty. 4.4.3 Adjacent Streets and Residential Yards Study Area Two different types of soil samples have been collected from the Adjacent Streets and Residential Yards Study Area: point samples (i.e., single point surface and subsurface samples, including soil and monitoring well borings) and MIS samples. Both point and MIS samples are used to delineate Adjacent Street ROW cleanup boundaries, whereas MIS samples alone are used to delineate Residential Yards cleanup boundaries. Soils represented by point samples will be removed from areas with concentrations greater than 1 mg/kg PCBs. Based on EPA's statistical evaluation of MIS sample triplicate data (Appendix L), EPA has directed that variability (as the upper confidence limit on the mean [UCL]) be incorporated into the establishment of CULs. Accordingly, soils represented by MIS samples will be removed from areas where the UCL is greater than 1 mg/kg. As described in Section 9.3.3.2, final soil excavation depths will be based on confirmation sampling to ensure that RvALs have been attained. As discussed in Section 3, dioxins and furans are designated as COCs in areas where they are co-located with PCBs above the PCB RvAL, per administrative direction by EPA (2009a). Based on the forensic work completed by the Dioxin Technical Workgroup and their 2008 and 2009 findings (Appendix M). Measurable concentrations of dioxins are always present in urban soils because of the contributions from various typical combustion and chemical sources. Elevated dioxin concentrations on the T-117 Upland Study Area have been documented. Potential T-117 sources that contribute contaminants to nearby streets and yards include the track-out of PCB- or dioxin-contaminated soil, air emissions from the burning of PCB- contaminated waste oils, and typical oil-fired furnace air emissions. Data from numerous studies assembled and evaluated by the Dioxin/Furan Technical Workgroup indicate that levels of dioxins in the neighborhood are higher than would be expected from typical urban sources, such as vehicle or residential emissions. Given the PCB concentrations measured in the Adjacent Streets and Residential Yards Study Area and the results of chemical pattern analyses for samples with concentrations of dioxins and furans, the contribution of direct PCB track-out to total dioxin concentrations appears to be small. The overall apportionment between T-117 and non-T-117 contributions, primarily related to potential air emission pathways, remains uncertain. Given this current uncertainty, dioxins and furans are not being used independently to define removal boundaries at this time. However, in areas where removal actions are required for PCBs, dioxins and furans will remain a COC and will be included as part of confirmation sampling for the Adjacent Streets and Residential Yards Study Area. This will eliminate the potential that any given street or yard area will have to be re-excavated, should the uncertainty about total T-117 contributions be resolved in the future. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 148 As discussed in Section 3, dioxins and furans are designated as COCs in areas where they are co-located with PCBs above the PCB RvAL, per administrative direction by EPA (2009a). Based on the forensic work completed by the Dioxin Technical Workgroup and their 2008 and 2009 findings (Appendix M), EPA has made the determination that the asphalt manufacturing facility operations were likely not the source of the majority of the dioxins and furans detected in the Adjacent Streets and Yards Study Area, and that the source of the dioxins and furans is as yet undetermined. However, based on an assumption that a minor portion of the dioxins and furans in the Adjacent Streets and Residential Yards Study Area may be associated with PCBs from asphalt manufacturing facility operations, EPA has directed that dioxins and furans be designated as COCs where co-located with PCBs above the PCB RvAL in the Adjacent Streets and Residential Yards Study Area (Appendix M). In summary, cleanup in the Adjacent Streets and Yards Study Area will be guided by the following assumptions: PCBs will beare the driver for streets and yards cleanup. Wherever PCB cleanup occurs, co-located dioxins will also be removed. Where PCB concentrations are below the PCB RvAL but dioxin/furan TEQs exceed the dioxin/furan TEQ RvAL, no cleanup will occur as part of this removal action. Post NTCRA PCB sampling will include analysis of dioxins and furans. Additional dioxin and furan data are expected to be generated as a result of additional sampling in the LDW, at adjacent upland sites, and in stormwater conveyance systems. These data will provide information to better identify dioxin and furan sources and upland soils concentrations in the area and will help put the dioxin and furan concentrations in the Adjacent Streets and Residential Yards Study Area into broader perspective with respect to sources and possible future removal actions. Removal areas for Adjacent Streets and Residential Yards, based on the distribution of PCBs, are shown on Figure 4-1. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 149 5 Recontamination Assessment The long-term effectiveness of the planned NTCRA at the T-117 EAA relies on the identification, characterization, and control of potential recontamination sources and pathways as they may exist after completion of the removal action. To assess this future recontamination potential, this section: Provides an overview of the source control strategy Establishes the baseline condition for a post-NTCRA T-117 EAA and discusses potential recontamination sources and pathways Critically evaluates the potential for these sources/pathways to contribute to the recontamination of post-NTCRA sediments Provides recommendations for multi-media monitoring to ensure long-term protectiveness of the remedy The recontamination assessment in this EE/CA is necessary to ensure that the potential for recontamination is addressed as part of the NTCRA design and through future source control actions by the responsible site owners, in coordination with the ongoing LDW-wide source control activities for the LDW Superfund Site. The potential for recontamination will also be considered in the design of post-NTCRA monitoring programs to help ensure the long-term effectiveness of the removal action. This assessment builds upon the initial evaluation presented in the draft EE/CA (Windward et al. 2008) and takes into consideration newly obtained site data for soil, catch basin solids, and groundwater. Also considered are the results of Ecology's recent sediment recontamination assessment for the Marina (SAIC 2009), and the investigation of soil and groundwater at the Basin Oil property (Ecology 2009b), and the findings of the sediment transport analysis presented in the LDW RI (Windward 2008) as it relates to the T-117 EAA. 5.1 OVERALL SOURCE CONTROL STRATEGY Source control for the T-117 EAA is governed by the strategy outlined for the LDW (Ecology 2004a). The goal of the LDW strategy is to minimize the potential for chemicals in sediments to exceed the LDW sediment cleanup goals and the SMS (WAC 173-204). Ecology is the lead agency implementing source control; Ecology works in cooperation with local jurisdictions and EPA, together forming the LDW Source Control Work Group (SCWG), to pursue this goal. The member agencies of the SCWG rely upon a variety of tools and strategies to encourage, implement, and monitor source control activities within the LDW and adjoining drainage basins, including public education, implementation of source-tracing programs, evaluation of potential upland and in-water contaminant sources, and enforcement of requirements Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 150 for the cleanup of contaminated sites and drainage systems that may have an ongoing or future potential to contaminate LDW sediment. Ecology's source control investigation findings and plans for implementing source control activities at the LDW Superfund Site are documented in various data gaps reports and source control action plans (SCAPs) (Ecology and SAIC 2008). The original SCAP for the T-117 EAA (Ecology 2005a) was published relatively early in the LDW source control process and, thus, did not include the results of later investigations and evaluations of groundwater and potential contaminant sources and pathways associated with the expanded T-117 EAA and adjacent properties (i.e., the Marina and Basin Oil property). Nonetheless, the T-117 EAA has continued to be a high priority for Ecology and the SCWG. The T-117 EAA SCAP identified storm drain outfalls and soil from Basin Oil, the former A&B Barrel, the T-117 Upland Study Area, and the Adjacent Streets as potential sources of recontamination to the sediment. Ecology recently completed a sediment recontamination assessment for the Marina (SAIC 2009) and site investigations at the inactive Basin Oil property (Ecology 2009b). Ecology also performed a facility review of Boeing South Park and determined that the likelihood of recontamination from stormwater discharges from parking lot runoff and noncontact cooling water from air conditioners to the LDW is low (Ecology 2004c). The City and the Port have also conducted source control-related activities, including the implementation of drainage controls, independent cleanup actions, catch basin monitoring, and bank stabilization of the T-117 shoreline. SubsequentOngoing source evaluation work by the Port and other SCWG members includes ongoing groundwater monitoring and the evaluation of the stormwater drainage system design and monitoring at the Marina. All of these post-SCAP activities and results are discussed in Section 2. SCAP activities identified but not yet completed include the verification of compliance with the NPDES permit requirements and the verification of catch basin drainages and discharge locations, connections to the sanitary sewer, and the presence of any septic systems. Ecology recently identified the ongoing EE/CA process as the principal vehicle for advancing source control for the T-117 EAA (Ecology and SAIC 2008). 5.2 POTENTIAL POST-NTCRA RECONTAMINATION SOURCES AND PATHWAYS The interrelationships between the potential pathways and associated source areas that may affect the post-NTCRA T-117 EAA are complex. Since the cessation of asphalt manufacturing operations in the mid-1990s, the potential for recontamination of soils has largely been restricted to the redistribution of existing contaminants. The NTCRA removal action described in this EE/CAs isare expected to remove the potential for recontamination to upland, street, and yard soils from this historical source. Thus, this section focuses on the potential for recontamination of post-NTCRA sediment. Figure 5-1 provides an overview of the potential sediment recontamination routes relevant to the T-117 sediment area after completion of the removal action. The T-117 Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 151 Upland Study Area and the Adjacent Streets and Residential Yards Study Area are either adjacent to or upgradient of the T-117 Sediment Study Area, which is located between RM 3.5 and RM 3.7 on the west side of the waterway within the LDW Superfund Site. The neighboring Marina and Basin Oil property are not geographically within the T-117 EAA but are considered to be potential upland source areas (referred to as RAAs). Although the NTCRA will not include the cleanup of these areas, they are evaluated in this EE/CA relative to their potential to contribute to the recontamination of the T-117 Sediment Study Area. and are thus included in this analysis inasmuch as they may serve as potential sources of recontamination to the EAA. The scope of work for the NTCRA (EPA 2007c) also stipulates that the RAAs must be considered in view of their recontamination potential. ia Deposition of airborne contaminants has been theorized for the T-117 EAA. King County (2008) has measured airborne deposition at various locations within the Duwamish corridor. However, no data are currently available to determine if urban and industrial sources not within the T-117 EAA are impacting the T-117 EAA and the rate at which airborne contaminants may be deposited at the site. Figure 5-1. Overview of post-NTCRA potential sediment recontamination source areas and routes at the T-117 EAA Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 152 Potential sources of COCs and pathways to the post-NTCRA T-117 EAA sediment discussed in this section include: Erosion and transport of onsite surface soil not isolated after the completion of the removal action Erosion and transport of surface or subsurface soil from adjacent properties Transport of contaminants via stormwater (including entrained soil/sediment and airborne contaminants) Migration and discharge of onsite and offsite contaminated groundwater from the T-117 EAA and RAAs to LDW sediment Transport and deposition of LDW sediment (upstream contributions and impacts from other removal actions)Transport and deposition of LDW sediment, including upstream contributions, and potential impacts from other nearby in--water actions that may occur prior to the implementation of the LDW remedy (e.g., a RCRA action or interim measure that addresses sediment adjacent to Boeing Plant 2) Sorption from LDW surface water Atmospheric deposition to the water surface and to surfaces in contact with stormwater discharging to the river The section is organized to first present the more localized potential sources and pathways (e.g., soil, groundwater) followed by larger-scale potential sources and pathways (e.g., upstream sediment, atmospheric deposition). The order in which the information is presented does not necessarily imply the relative importance of the pathway. Figure 5-2 presents a conceptual view of the potential pathways that are discussed further in this section. Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 153 Slipsheet for (11x17) Figure 5-2. T-117 EAA possible post-NTCRA recontamination routes Lower Duwamish Waterway Superfund Site: EE/CA DRAFT T-117 Early Action Area FINAL January 19June 3, 2010 Page 155 5.2.1 Erosion and transport of surface soil This section provides a discussion of the potential for sediment recontamination via surface soil erosion from each of the upland source areas, including the T-117 Upland Study Area, Adjacent Streets and Residential Yards Study Area, the Marina, and Basin Oil property. Post-NTCRA T-117 EAA sediment could potentially be recontaminated through bank erosion and stormwater transport of contaminated surface soils from upland source areasnot otherwise addressed through the removal action or postremoval action monitoring and controls. 5.2.1.1 T-117 Upland Study Area soil As part of the T-117 EAA NTCRA, contaminated surface, shallow subsurface, and bank soils will be removed and disposed of offsite, and the removal areas will be backfilled with clean soil or covered with clean fill or capped if they are located within the intertidal area. Therefore, upon completion of the NTCRA, the potential for any remaining soils from the T-117 Upland Study Area to impact LDW sediment quality will be significantly reduced if not eliminated. Residual contaminants, if present, would be located at depth and are expected to be at concentrations below their respective RvALs or will be capped. Measures will be taken to isolate any remaining subsurface contaminants that might be exposed through modified site topography. This isolation will be achieved through soil excavation and, where necessary, through the placement of clean, imported backfill materials to establish the post-NTCRA topography. This removal and isolation action is particularly important in areas where the final site use may include enhanced aquatic habitat and where the upland topography will be lowered to increase the intertidal surface area. In summaryThus, the NTCRA willis being designed to ensure the effective long-term isolation of any remaining contaminants in soils in the T-117 Upland Study Area. 5.2.1.2 Adjacent Streets and Residential Yards Study Area soil The adjacent streets and residential yards that have been cleaned up are expected to be minorimal sources of PCB contribution to the T-117 Sediment Study Area. Soil from some yards with elevated dioxin/furan concentrations will not be removed as part of this cleanup action. PCB and dioxin/furan concentrations are elevated around two of the T-117 Upland Study Area catch basins (CB-3 and CB-5). To date, the source of these contaminants has not been identified, and further investigations is being conducted. The possibility that the contaminants may have come from the Adjacent Streets and Residential Yards Study Area has not been ruled out. When the removal action in the Adjacent Streets and Residential Yards Study Area is complete, the concentrations of contaminants in stormwater that dischargesing to the T-117 Sediment Study Area may resemble those in stormwater from similar LDW stormwater sub-basins. This possibility will be confirmed through subject to empirical Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 157 sampling verification. The erosion of surface soils from yards and unpaved street shoulders in the Adjacent Streets and Residential Yards Study Area, with subsequent transport to the T-117 Sediment Study Area or CSS, has also been identified as a potential post-NTCRA recontamination pathway. Although soils entrained in stormwater flows could reach the LDW through various storm drain systems that discharge to the waterway (see Section 5.2.2.2), this post-NTCRA pathway is expected to be minimal because of street pavement and vegetative cover in the yards. Recent independent cleanup actions for the Adjacent Streets (Integral 2006b) have included the paving of streets and either the paving of the gravel shoulder areas or removal of contaminated material in the unpaved road shoulders and replacement with clean gravel. NTCRA cleanup actions for the Adjacent Streets will include the removal and offsite disposal of remaining contaminated soil. Where soil is removed, these areas will be backfilled with clean soil resulting in the attainment of RvALs in the remaining surface or near-surface soil. Upon completion of the NTRCA, the majority of the Adjacent Streets will be repaved and curbed to meet current City design standards, greatly minimizing the potential for the transport of residual low-level surface soil contaminants from this area. In addition, these actions should greatly limit the potential for wind-erosion of surface soils. 5.2.1.3 South Park Marina soil In 2007 and 2008, Ecology collected soil, sediment, and groundwater samples at the Marina. As described in the subsequent recontamination assessment report (SAIC 2009), the sampling focused on the location of a former disposal pond associated with the former A&B Barrel recycling facility on the Marina property. Work included the advancement of 16 soil borings to depths that rangeding from 2.5 to 20 ft. Ecology reported a number of exceedances of MTCA CULs as well as draft soil-to-sediment and groundwater-to-sediment SLs developed by Ecology for COCs at the Marina. Subsequent to this data collection work and initial screening, Ecology concluded that the potential for these COCs to reach the LDW was not clearly established. For example, groundwater showed only limited exceedances of Ecology's CULs and draft SLs. As stated in the recontamination assessment report (SAIC 2009), river bank soil samples also had a number of exceedances, but the link between these COCs and those in the intertidal sediment was uncertain. In order to evaluate and resolve these uncertainties, a sediment recontamination assessment was conducted (SAIC 2009). completed a sediment recontamination assessment for the Marina (SAIC 2009) based on the results of soil, groundwater, and sediment sampling activities conducted in 2007 and 2008. The investigation identified a number of contaminants with concentrations in soil that exceeded MTCA CULs and draft soil-to-sediment and groundwater-to-sediment SLs used by Ecology and described in the investigation report (SAIC 2009). The sampling focused on the location of a former disposal pond in the vicinity of the Marina and included the advancement of 16 soil borings to depths ranging from 2.5 to 20 ft. Although the presence of elevated contaminant Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 158 concentrations in upland soil was documented, it was unknown whether these soils could migrate to the LDW. Therefore, a quantitative recontamination assessment was undertaken using a conservative fate and transport analytical model (SAIC 2009). Results showed that any potential erosion and transport of COCs in soils from the Marina would have little effect on COC concentrations in the post-NTCRA T-117 EAA sediment. Table 5-1 presents the soil and groundwater COCs identified and evaluated by Ecology in their source control study of the Marina. Table 5-1. Concentrations of Contaminants of concern COCs identified by Ecology for at the Marina compared with T-117 Upland Study Area removal action levels Maximum T-117 Upland Maximum T-117 Upland Concentration in Study Area Concentration in Soil Study Area a a Groundwater (ug/L) Groundwater (mg/kg) Soil RvALs b b COCs Min Max RvALs (ug/L) Min Max (mg/kg) Metals Arsenic 1.56 8.07 5 1.0 9.410.8 7.3 Cadmium 0.022 0.091 NSns 0.021 31.4 ns Chromium 1.31 40.4 NSns 6.04 465 ns Copper 2.83 9.83 3.4ns 5.43 198 ns Lead 0.192 0.519 ns 1.18 3180 ns Mercury 0.00115 0.001569 ns 0.004 29.5 ns cb Silver 0.01 U 0.005 1.9 0.038 0.299 2.0/400 Zinc 2.93 5.2 ns 14.8 1,510 ns PCBs d Total PCBs 0.2 U 0.21 U 0.01 0.0059 36 0.65/1.0 PAHs cPAH TEQ nc Unc 0.15 0.0017 1.01 0.14008 TPH Gasoline-range U ns U ns organics Diesel-range e 0.2 U 0.21 UU 500 1.8 U 2312,000 J 200/2,000 organics Residual-range e 0.2 U 0.21 UU 500 6.5 U 2127,000 J 200/2,000 organics a Source: SAIC (2008). b Soil RvALs as defined in Section 4. c The TEE-based RvAL is 2.0 mg/kg in the upper 0 to 6 ft of soil for areas where the terrestrial ecological exposure scenario defined under MTCA is applicable. The RvAL is 400 mg/kg for soils deeper than 6 ft. d TEE-based RvAL is 0.65 mg/kg in the upper 2 ft of soil for areas where the terrestrial ecological exposure scenarios defined under MTCA is applicable. The RvAL is 1.0 mg/kg for soils deeper than 2 ft. e TEE-based RvAL is 200 mg/kg in the upper 0 to 6 ft of soil for areas where the terrestrial ecological exposure scenario defined under MTCA is applicable. The RvAL is 2,000 mg/kg for soils deeper than 6 ft. COC contaminant of concern RvAL removal action level Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 159 DDD dichlorodiphenyldichloroethane SAIC Science Applications International Corporation DDE dichlorodiphenyldichloroethylene SVOC semivolatile organic compound DDT dichlorodiphenyltrichloroethane TEE terrestrial ecological evaluation MTCA Model Toxics Control Act TPH total petroleum hydrocarbons nc not calculated U not detected at given concentration ns not specified VOC volatile organic compound PCB polychlorinated biphenyl Ecology's recontamination assessment (SAIC 2009) considered the erosion of bank contaminants and the migration of COCs in groundwater to LDW sediment. The recontamination assessment concluded that COCs associated with soil at the Marina might cause recontamination of the LDW if soil particles were to eroded and be transported to the LDW by stormwater. The owners of the Marina recently provided a map of the storm drain system at the Marina (Crow 2010). The quality of storm solids in the facility's catch basins that could eventually be transported to the T-117 Sediment Study Area will be assessed during the removal action design phase (See Section 9.4). If the stormwater pathway is determined to poses a risk of sediment recontamination, additional soil erosion and/or stormwater controls or monitoring will be required. These will be developed in cooperation with the Marina owner and in consultation with Ecology. 5.2.1.4 Basin Oil property soil Ecology initiated an investigation of surface and subsurface soil and groundwater conditions at the Basin Oil property in 2009 through the collection of 10 soil borings to depths of 14 to 16 ft at various locations throughout the property (see discussion of Basin Oil investigation sampling locations and results in Section 2.4.1). Soil samples from the 0-to-6-in. depth were analyzed, and many of the COCs identified for the T-- 117 Sediment Study Area (PCBs, TPH, PAHs, phenol) were detected. Boring logs from the investigation indicated the presence of slight to moderate sheens at some borehole locations in shallow soils (1 to 2 ft) and again at the 7-to-8-ft depth range. These sheens were likely associated with the detectable organic vapors recorded using field instrumentation, as noted on the boring logs. Soil samples from the near-surface interval (0-to-6-in. depth) and the deepest interval from each boring were submitted for analysis; the remaining samples were archived. Petroleum hydrocarbons (i.e., diesel, lube oil, and gasoline-range organics) were detected in the near-surface soil samples, particularly at boreholes BSB-6 through BSB- 10. PAHs were also detected in the shallow soil from borehole BSB-1. Gasoline-range organic compounds and LPAHs were detected in shallow soil samples from BSB-7 and BSB-10. Other contaminants detected at the Basin Oil property included PCB Aroclor 1260, BEHP, arsenic, and dioxins and furans. As described in Section 3.3.4, Basin Oil groundwater and soil data (Ecology 2009b) were screened using the SLs developed for the T-117 EAA in Section 3.3.2. Concentrations of arsenic, total PCBs, TPH, nickel, cPAHs, ethylbenzene, xylenes, and carbazole were greater than their respective SLs in Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 160 Basin Oil soil. However, the concentrations of these contaminants were below soil RvALs (Section 4.3.3), and thus, the contaminants from this RAA do not pose a potential for recontamination of T-117 soil. No PCB concentrations were detected in surface soil, and the highest dioxin/furan TEQ was 1.59 ng/kg; thus, the contaminants from this RAA do not pose a potential for recontamination of T-117 sediment. 5.2.1.5 Soil pathway summary and post-NTCRA monitoring recommendations The activities to be completed as part of the NTCRA as well as those planned for the Adjacent Streets and Yards are expected to eliminate the potential for surface soils to recontaminate post-NTCRA T-117 EAA sediment at concentrations above the proposed RvALs. In addition, evaluations of recontamination potential from soils from the Marina and Basin Oil property indicated a low potential for LDW PCB recontamination of T-117 sediment recontamination from these sources. A plan for monitoring stormwater solids and sediment quality after the removal action will be developed and implemented. The plan will include adaptive management response measures to be implemented in the event monitoring data indicate the potential for sediment recontamination. 5.2.2 Stormwater transport As discussed in Section 5.2.1, one pathway for contaminants to reach the T-117 Sediment Study Area is via stormwater runoff. Urban runoff carries contaminants from various sources, including soil, fertilizers and pesticides from yards and gardens, spills, drips from automobiles, tire wear, road surface wear, and atmospheric deposition. Available information regarding stormwater runoff from the T-117 Upland Study Area, Adjacent Streets and Residential Yards Study Area, the Marina, and Basin Oil property is discussed below. 5.2.2.1 T-117 Upland Study Area stormwater Historically, contaminated surface soils within the T-117 Upland Study Area likely served as a source of contamination to the LDW via several pathways, including the stormwater pathway (Ecology 2005a). More recently, much of the T-117 Upland Study Area, except the upper bank area immediately east of the edge of the T-117 Upland Study Area pavement, has been paved, isolating most of the underlying contaminated soils from stormwater. In the future, and as discussed above in Section 5.2.1.1, planned NTCRA actions will include the removal of upland soils with COC concentrations greater than the RvALs followed by backfilling or capping with clean materials. Nevertheless, stormwater runoff will continue to originate on the surface of the T-117 Upland Study Area. This runoff will discharge to the LDW through existing or newly constructed conveyances, swales, and outfalls; via sheet flow or infiltration through permeable surfaces (e.g., vegetated or gravel-covered shoreline areas). Stormwater could become contaminated through the deposition of regional airborne contaminants (as discussed in Section 5.2.6) or as a result of future onsite activities. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 161 PCBs, PAHs, dioxins and furans, and some metals were detected in recent (2009) solids samples collected within and adjacent to catch basins CB-3 and CB-5 (Map 2-1). Some of the contaminants (i.e., PCBs and PAHs) in theThe contaminated solids adjacent to the catch basin could have potentially originated from atmospheric deposition because these same contaminants have been observed in atmospheric deposition samples elsewhere in the Duwamish corridor (King County 2008) or from surface soil at the top of within the T-117 unpaved bank at the east side of the T-117 Upland Study Area. The NTCRA will remove any T-117 Upland Study Area sources through the remediation of contaminated surface soils. In addition, new drainage systems for the T-117 Upland Study Area will be designed to include BMPs for retaining solids (e.g., sumps, swales, or filters) and will be required to meet the City code as described below for the Adjacent Streets and Residential Yards Study Area. Solids that accumulate in these new drainage systems will also be monitored for COCs as described further in Section 9.4 5.2.2.2 Adjacent Streets and Residential Yards Study Area stormwater Following cleanup of the Adjacent Streets and Residential Yards, a permanent drainage system will be constructed to collect and treat runoff from the approximately 1.7-ac area that is currently served by the temporary system that was installed by SPU as part of the interim cleanup that occurred in December 2004 (Map 2-2). This area includes approximately 1.1 acres of public ROW in the triangle-shaped area formed by the intersections of 17th Avenue S, Dallas Avenue S, and S Donovan Street, as well as about 0.6 acres of private property (Basin Oil and the hillside adjacent to S Donovan Street). Treated runoff from this area will be discharged to the T-117 Upland Study Area as it was prior to the 2004 interim cleanup. Runoff from the Residential Yards outside this area that will be affected by the cleanup will continue to be discharged to the combined sewer system (Map 2-2). Samples collected to date from streets and catch basins adjacent to T-117 indicate that except for PCBs, the concentrations of other LDW contaminants of concern are comparable to those found in urban streets and storm drains sampled throughout the LDW. As described in Section 2.3.3.1, elevated concentrations of PCBs were found in ROW soils in 2004, which led SPU to conduct an interim action to protect residents in the area from being exposed to PCBs by removing and/or capping the PCB- contaminated soil. Recent samples collected from the temporary drainage system indicate that the 2004 interim cleanup has been effective in containing PCBs. Table 5-2 compares the results for sediment samples collected from catch basins in roadways adjacent to T-117 with the results from 124 to 133 ROW catch basins throughout the LDW (number of samples varies depending on the parameter analyzed). These LDW ROW catch basin samples are considered to be representative of the stormwater solids that will originate from the roadways in the vicinity of the T-117 EAA following the NTCRA. As shown in Table 5-2, concentrations in samples from the temporary storm drains generally fall within the lower range of concentrations detected in other Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 162 roadway samples. The samples collected from the Dallas Avenue S storage tanks contain higher levels of metals, but because these samples contained a large amount of rust from weathering of the tanks, they are probably not representative of metals concentrations in the roadway solids. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 163 Table 5-2. Stormwater sampling results T-117 Temporary Storm Drain System Sampling Locations and Dates Lower Duwamish ROW Catch Basinsc Concentrations CB3-DAL SW1/ SW1/ Concentrations CB1-DAL CB2-DAL CB2-DAL (CB) Tanks Tanks RCB 101 CB4-DAL b SQS/ CSL/ (CB) (CB) (CB) 03/22/05 (Tank) (Tank) (CB) (CB) b b a b Contaminant Unit LAET 2LAET 03/22/05 03/22/05 03/10/10 05 02/25/08 03/10/10 03/14/07 03/10/10 n Min Max Median Mean Arsenic mg/kg dw 57 93 na na 10 U na 20 30 U 7 U 8 129 3 750 9 18 Copper mg/kg dw 390 390 na na 147 na 472 284 50.6 143 128 9.1 4,520 99 168 Lead mg/kg dw 450 530 na na 237 J na 450 250 J 22 67J 129 4 3,690 89 168 Mercury mg/kg dw 0.41 0.59 na na 0.08 na 0.08 U 0.33 0.05 U 0.04 129 0.02 2.2 0.07 0.17 Zinc mg/kg dw 410 960 na na 571 na 1,890 1,040 237 588 128 58 3,650 333 464 TPH diesel mg/kg dw 2,000d nc na na 530 na na 900 730 U 75U 124 35 6,800 370 917 TPH oil mg/kg dw 2,000d nc na na 2,300 na na 3,500 4,100 550 124 110 20,000 2,350 3,669 Total LPAH g/kg dw 5,200 13,000 na na 3,270 J na 120 1,100 J 180 J 110 133 14 8,900 310 895 Total HPAH g/kg dw 12,000 17,000 na na 8,060 J na 1,272 7,480 J 1,160 1,226 J 133 42 36,520 1,603 3,768 BEHP g/kg dw 1,300 1,900 na na 21,000 na 6,200 18,000 2,500 1,600 J 126 24 36,520 1,957 3,977 Total PCBs g/kg dw 130 1,000 23,000 14,000 420 NJ 3,900 350 620NJ 310 560 NJ 133 10 23,000 64 670 a Catch basins cleaned after sampling. b Same as CB4-DAL. c Samples collected from catch basins located in the right-of-way throughout the Lower Duwamish Waterway study area. Non-detected values are included in the summary statistics at their detection limits. d MTCA Method A soil CUL for unrestricted use. BEHP bis(2-ethylhexyl) phthalate LPAH low-molecular-weight polycyclic aromatic hydrocarbon CB catch basin N tentative identification (presence or identity of the analyte is in doubt and the CSL cleanup screening level reported concentration is estimated) CUL cleanup level na not analyzed dw dry weight nc no criteria HPAH high-molecular-weight polycyclic aromatic hydrocarbon PCB polychlorinated biphenyl J estimated concentration ROW right-of-way LAET lowest apparent effects threshold SQS sediment quality standards 2LAET second lowest apparent effects threshold U not detected at given concentration Boldidentifies detected concentrations. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 164 As discussed in Section 2, runoff from the portion of the Adjacent Streets and Residential Yards Study Area located just east of 17th Avenue S (approximately 1.7 acres) is a potential post-NTCRA recontamination pathway to the T-117 Sediment Study Area (Figure 5-2). Runoff from this area is currently collected and conveyed by a temporary stormwater system to storage tanks, where it is subsequently released at a controlled rate to the CSS at 17th Avenue S and S Donovan Street (Section 2.2). The City obtained discharge authorization from the King County Industrial Waste Program for this discharge; as part of the authorization, SPU tests the quality of water discharged to the CSS every month in which discharges occur. Since 2005, PCBs have been detected once (in January 2008) in the runoff collected by the temporary system at a concentration of 0.12 g/ L (Appendix C). This detection does not represent a recontamination concern to the LDW because it is an isolated detection and the reported concentration was only slightly above the method detection limit. The majority of the stormwater represented by this sample was discharged to the CSS, which is conveyed to the County's wastewater treatment plant. After the NTCRA, the temporary stormwater system will be replaced with a permanent collection and treatment system, and runoff from the entire area currently served by the temporary system will be discharged to the LDW in the vicinity of the T-117 EAA. The new system will be designed in accordance with the SMC 22.800 and the Seattle Department of Planning and Development Director's Rules (City of Seattle 2009a), which establish specific requirements and procedures for designing and constructing facilities that treat stormwater prior to release to adjacent surface waters. The potential for runoff from the Adjacent Streets and Residential Yards Study Area to be a significant source of recontamination to post-NTCRA T-117 EAA sediment is therefore considered to be limited by the above-described controls. In addition, previous remediation efforts at residential yards and planned paving upgrades will greatly limit the potential for stormwater contamination from this area, thus controlling contaminants that might otherwise reach post-NTCRA T-117 EAA sediment at concentrations above selected RvALs. Runoff from the remainder of the Adjacent Streets and Residential Yards Study Area (generally west of 17th Avenue S) is directed to the CSS, which occasionally overflows to the LDW. The nearest CSO (operated by the County) is located at 8th Avenue S and discharges to the LDW approximately 3,800 ft downriver of the T-117 EAA. County records show that this CSO has not overflowed in the past 10 years. Contaminants from this area (primarily from the road shoulders on 16th Avenue S and S Donovan Street) could become entrained in stormwater that discharges to the CSS. Although the cleanup is expected to significantly reduce or eliminate PCB discharges to the CSS, it is likely that TPH, PAHs, and metals, which are commonly found in urban runoff in the Study Area and other urban areas in the vicinity, will remain at concentrations typical of urbanized environments. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 165 After the cleanup and removal of PCB-contaminated soil in the ROW, runoff from the Adjacent Streets is expected to be similar in quality to runoff from other urban areas and as such can be managed in accordance with existing City stormwater management program/policies and the City's NPDES municipal stormwater permit. In 2009, the City updated its stormwater code (SMC 22.800) and associated technical manuals (City of Seattle 2009a) to comply with its NPDES permit. Ecology has reviewed and approved both as being equivalent to the Stormwater Management Manual for Western Washington (Ecology 2005b). The method of treating runoff from the Adjacent Streets will be determined during design. Options include biofiltration swales, filter strips, bioretention cells, wet vaults, and media filtration. These treatment technologies have all been approved by Ecology for urban stormwater treatment and are considered to be effective in removing 80% or more of the total suspended solids present in stormwater (Ecology 2005b). Because many of the pollutants typically found in urban runoff (e.g., metals, petroleum hydrocarbons and other organic compounds) are hydrophobic and tend to adsorb to particulates, these treatment systems are also effective in removing other pollutants. Considering that treatment will be applied and given the relatively small drainage area (1.7 ac), the post- project stormwater pollutant loadings to the T-117 Sediment Study Area from the Adjacent Streets will be low. Therefore, the potential for T-117 sediments to recontaminate after cleanup is expected to be low. Post-remedial monitoring of the T-117 Sediment Study Areas and stormwater solids will provide an indication of how effective upland actions in the Adjacent Streets and Residential Yards Study Area have been. For all contaminants, not just PCBs, stormwater monitoring results will be compared with a range of regulatory and guidance values to evaluate the presence and relative scale of this line of evidence and the potential for recontamination. Decisions regarding the need for additional source control, such as increased BMPs or additional treatment, will be made in consideration of needed load reduction estimates. 5.2.2.3 South Park Marina stormwater Ecology's sediment recontamination assessment of the Marina (SAIC 2009) evaluated the potential for post-NTCRA T-117 EAA sediment to be recontaminated by COCs identified at the Marina through erosion and groundwater the stormwater discharge pathway. The quantitative assessment used an analytical model, which generally concluded that the stormwater transport of COCs from the Marina has had and will continue to have little effect on COC concentrations in T-117 EAA sediment. Although the assessment did not specifically include the sampling of solids from the Marina catch basins,Thus, COC loading from the Marina is expected to be minimal, in part because the southern-most catch basin at the Marina discharges through a general stormwater NPDES-permitted shoreline outfall fitted with an oil/water separator and a sand filter (StormwateRx) (see Section 2). Required monitoring of this outfall by the Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 166 Marina owner will provide limited information to support the assessment of this potential pathwaye long-term effectiveness of the NTCRA. I However, it is generally recognized that NPDES monitoring may not always address all COCs that may need to be considered to protect LDW sediment. Post--NTCRA monitoring of the T-117 sediment removal area should detect recontamination that may originate from this potential source. The stormwater system at the Marina has not been completely mapped, and this is currently a data gap relative to the complete evaluation of this RAA. Additional work will be performed prior to the NTCRA to characterize the stormwater conveyance system at the Marina and to verify stormwater drainage areas and points of discharge (i.e., to the LDW or the CSS). 5.2.2.4 Basin Oil property stormwater Information regarding the quality of surface soil at the Basin Oil property is provided in Section 2.4.1. As discussed in Section 5.2.1.4, petroleum hydrocarbons and other contaminants were detected in surface and near-surface soil samples collected by Ecology. Currently, runoff from the property is largely contained onsite because of excavation activities that have prevented most runoff from exiting the property. Only the driveway entrances currently drain offsite. In the future, unconfined contaminated surface soil, contaminants associated with future activities at this site, or airborne deposited materials at the Basin Oil property will have the potential to reach the post- NTCRA T-117 EAA sediment via the storm drain infrastructure planned for portions of the Adjacent Streets and Residential Yards Study Area. This new stormwater conveyance will eventually discharge to the LDW in the vicinity of the T-117 Sediment Study Area. In order tTo prevent potential sediment recontamination, contaminated surface and subsurface Basin Oil soil s at the Basin Oil property must be addressed bywill be cleaned up (e.g., by removal or capping) before the NTCRA. If this is not feasible and soil can only be addressed post-NTCRA, additional care and source control measures will be needed. Once the site owner (e.g., through removal, capping) in consultation with Ecology before the NTCRA occurs. When these soils have been addressed, it is expected that the property will be a minimal source of contamination to sediments. 5.2.2.5 Stormwater pathway summary and monitoring recommendations TThe preceding discussions indicate that it is unlikely that post-NTCRA T-117 EAA sediment will be contaminated at concentrations above the RvALs as a result of stormwater discharge. New stormwater systems installed at the site will be required to meet the treatment requirements of SMC 22.800 and the SPU Director's Rule 20-005 (SPU), 17-2009 (DPD) (City of Seattle 2009a) that sets forth specific source control measures under the code. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 167 Storm drain solids in the new stormwater system will also be monitored to verify that site-related contaminants are not present at elevated concentrations. The potential for the enrichment of contaminants in the finer-fraction soils and the increased potential for the transport of fine-grained materials will be considered in the selection of monitoring and analytical approaches. Planning for this monitoring will be included in the long-term post-NTCRA monitoring plan for the T-117 EAA. Monitoring in the Adjacent Streets and Residential Yards Study Area may be supplemented by accomplished as part of the City's source- tracing program, which that is conducted in collaboration with the LDW SCWG. Details of the monitoring program for the T-117 EAA will be tailored to the specific design of the stormwater conveyances. In addition, T-117 EAA sediments in the vicinity of stormwater discharges may will be monitored as part of the long-term sediment monitoring plan. 5.2.3 Groundwater discharge After completion of the NTCRA, groundwater will continue to discharge to the T-117 Sediment Study Area and could potentially be a pathway for recontamination of post- NTCRA T-117 EAA sediment. The potential for this pathway to recontaminate post- NTCRA sediment is discussed in detail in Appendix B and summarized in the following subsections. 5.2.3.1 T-117 Upland Study Area groundwater As part of the NTCRA, contaminated surface and subsurface soil will be removed from the T-117 Upland Study Area to meet the RvALs at the specified compliance depths detailed in Section 4. This removal will greatly reduce the potential for residual soil contaminants to partition to groundwater. Even under current conditions at the T- 117 Upland Study Area, the potential for contamination of sediment via groundwater discharge is low (see Appendix B), and this will be verified through groundwater monitoring (see Section 5.2.3.5). These empirical data and lines of evidence demonstrate that groundwater is not causing sediment recontamination under current conditions. It can therefore be inferred that groundwater will not result in sediment recontamination after contaminated soils have been removed from the upland site. 5.2.3.2 Adjacent Streets and Residential Yards Study Area groundwater Information on the concentrations of contaminants in groundwater beneath this area is limited. However, given the nature and extent of the contamination within the Adjacent Streets and Residential Yards Study Area (i.e., shallow soils contaminated primarily with PCBs and dioxins and furans) and the planned removal of contaminated soil as part of the NTRCA, it is unlikely that water infiltrating through any exposed soils (i.e., lawns or street ROW soils) will leach contamination to groundwater (Appendix B). Thus, it is unlikely that contamination transported via the groundwater pathway from the Adjacent Streets and Residential Yards Study Area will impact the post-NTCRA T-117 EAA sediment above the RvALs. The need for The Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 168 number and placement of additional wells in Adjacent Streets will be evaluated during the NTCRA design phase. 5.2.3.3 South Park Marina groundwater As discussed above, Ecology recently completed a sediment recontamination assessment of the Marina as part of its lead role for implementing source control in the LDW (SAIC 2009). The assessment concluded that groundwater transport from the Marina is predicted to have little effect on sediment. Sediment sampling in 2008 verified that elevated Marina groundwater contaminants (i.e., arsenic, dieldrin, tetrachloroethylene [PCE], and mercury) were not elevated in the adjacent Marina sediment (SAIC 2008); only PCB concentrations in the Marina sediment were elevated above the RvALs. In addition, a net groundwater flow map (Map 2-75) was prepared for the T-117 Upland Study Area based on the March 2008 tidal study. This assessment indicated that groundwater generally travels in an east-northeast direction. Based on groundwater flow direction and the contaminant distribution at the Marina, it is unlikely that groundwater is migrating from the Marina to the T-117 Upland Study Area. Thus, any COC loading in groundwater from the Marina is not expected to contaminate T-117 EAA groundwater or recontaminate post-NTCRA sediment at concentrations above the RvALs. 5.2.3.4 Basin Oil property groundwater Groundwater samples were collected by Ecology from monitoring wells MW-12 and MW-13, which were installed next to the Basin Oil property on the 17th Avenue S and S Donovan Street ROWs, respectively (see Map 2-4039, Section 2.4.1). Dissolved arsenic was detected in all samples at concentrations that ranged from 9.4 to 20.4 g/L. Similar groundwater monitoring results have been reported for downgradient monitoring wells MW-01, MW-09, MW-10 and MW-11. Arsenic, copper, and BEHP were detected in one or more wells, and low concentrations of PCBs and TPH-D were detected in monitoring wells MW-1 and MW-10, respectively, based on recent groundwater monitoring of these wells by the Port and the City. However, tThese concentrations of detected contaminants are not indicative of a concentrated upgradient source and thus indicate a low likelihood of recontamination of post- NTCRA sediment. 5.2.3.5 Groundwater pathway summary and monitoring recommendations Based on available sampling, and monitoring data evaluated in Appendix B, and the results of independent recontamination analyses for areas upgradient of the T-117 Sediment Study Area, it is unlikely that post-NTCRA T-117 EAA sediment will be contaminated at levels above the established RvALs via groundwater transport. Nevertheless, the potential for groundwater transport of COCs to the T-117 Sediment Study Area will be considered evaluated during the development of the NTCRA Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 169 design and the long-term effectiveness monitoring program. Post-NTCRA groundwater monitoring and long-term performance monitoring of the T-117 Sediment Study Area is discussed further in Section 9.5. As part of the program, long-term groundwater and sediment monitoring will be implemented following the NTCRA to ensure that the groundwater flowing to and through the T-117 Upland Study Area is not a source of recontamination. The post-NTCRA long-term monitoring program will likely include a monitoring well network upgradient of the restored T-117 shoreline to monitor groundwater quality prior to discharge to the LDW. 5.2.4 In-waterway sediment transport and deposition As discussed in Section 5.2, oOne pathway for contaminants to reach the T-117 Sediment Study Area is via transport and deposition of LDW sediment. Sediment may be transported from upstream areas and/or nearby areas subject to sediment removal actions. The T-117 Sediment Study Area is located in the LDW, an estuarine system that is influenced by the Upper Duwamish/Green River. A great deal of sediment from this river is being deposited within the LDW. To estimate the influence of this transport and deposition on an LDW-wide scale, sediment transport dynamics within the LDW (including the T-117 Sediment Study Area) have been modeled as part of the LDW RI to estimate area-specific net erosion rates and maximum scour depths during highflow events, net sedimentation rates, and bed replacement dynamics (Windward 2008; QEA 2008). This modeling is currently being used in the LDW FS (ENSR|AECOM 2009) to predict changes in chemical concentrations in sediment over time and can also be used to estimate the future influence of the Upper Duwamish/Green River on sediment composition in the river segment (RM 3.5 and RM 3.6) that includes the T-- 117 Sediment Study Area. At the end of the 30-year modeling period, 75 to 100% of the sediment within this segment and the channel-side half of the area between RM 3.6 and RM 3.7 was estimated to be replaced with sediment from the Upper Duwamish/Green River. Thus, this general area is predicted to take on the characteristics of the sediment being depositing from the river over Howevertime. However, an assessment of sediment deposition or erosion within the spatial scale of the T-117 Sediment Study Area based on LDW-wide or reach-specific model predictions hasmay have a high level of uncertainty, and can only should be only be consideredused as one line of evidence to assess future conditions, and is not a substitute for post- removal action sediment monitoring. As shown in Figure 5-3, greater than 99% of the sediment load to Reach 2b, where the T-117 EAA is located, was estimated to come from the Upper Duwamish/Green River system (QEA 2008). Mean contaminant concentrations in sediment in this upstream Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 170 area (1.7 mg/kg OC total PCBs, 6.8 mg/kg dw arsenic, 51 g/kg dw cPAH TEQ)15 are much lower than sediment RvALs. Thus, post- NTCRA sediment deposition from upstream should not result in recontamination of the T-117 EAA to levels that exceed the selected RvALs. Figure 5-3. Schematic of the net LDW sediment transport processes over a 30-yr period Based on the sediment transport modeling, the T-117 Sediment Study Area was identified in the LDW RI (Windward 2008) as having the following conditions and characteristics: Between RM 3.5 and RM 3.6, the sediment area was characterized as a net depositional environment with a net sedimentation rate > 3 cm/year. From RM 3.6 to RM 3.7 in the nearshore, the sedimentation rate was estimated to be much lower (0 to 0.5 cm/year). The net erosion rate during high-flow events (2- to 100-year flood events) was estimated to range from 0 to 6 cm/year in the area between RM 3.6 and RM 3.7, with maximum scour depths up to 6 cm. Less than 1% of sediment deposited within the T-117 Sediment Study Area was estimated to originate from lateral sources. At the end of the 30-year modeling period, 75 to 100% of the sediment between RM 3.5 and RM 3.6 and the channel-side half of the area between RM 3.6 and RM 3.7 was estimated to be replaced with sediment from the Upper Duwamish/Green River. 15 Note that these concentrations are based on data presented in the RI (Windward 2008); additional data have been collected since that time and are being evaluated. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 171 Thus, this area is predicted to take on the characteristics of the sediment being depositing from the river over time. In contrast, only 0 to 25% of the nearshore sediment between RM 3.6 and RM 3.7 was estimated to be replaced with sediment from the Upper Duwamish/Green River, indicating little bed replacement. Contaminated areas in the LDW will be addressed through sediment remediation and source control actions (which could involve actions such as bank remediation) following the issuance of the ROD for the LDW. However, the relative sequencing of other actions and the T-117 EAA NTCRA has not yet been established. If areas near or upstream of the T-117 EAA are addressed after the NTCRA, these actions could potentially recontaminate T-117 EAA sediment, particularly if these areas are dredged. Dredging tends to re-suspend sediment, some of which may be transported outside of the dredging footprint. Sediment transport modeling to specifically assess the potential for contamination of the T-117 EAA during or following the remediation of nearby areas has not been conducted. However, it is expected that any remedial actions carried out at nearby areas will include measures to minimize the potential for contaminants to spread during remedial actions. Sediment and water quality monitoring will also likely be required during all remedial activities, and postremediation monitoring programs willshould be designed to not only assess the effectiveness of the remedial actions carried out at nearby areas but also ensure that post-cleanup residuals from those projects do not affect neighboring areas (e.g., the T-- 117 Sediment Study Area). 5.2.5 Surface water transport within the LDW Sources of COCs to surface waters of the LDW include maritime activities, which can occasionally result in releases of fuel and other hazardous materials, and a variety of other upland/lateral sources, including regional stormwater discharges and CSOs. Depending on the location and nature of these releases, they could potentially provide a source of recontamination to T-117 EAA sediment after the completion of the NTCRA. However, present-day maritime practices, rapid spill response resources, regulatory requirements, and municipal/industrial wastewater discharge limits have been established to control and/or eliminate these types of releases to the LDW. Thus, it is unlikely that they would contaminate post-NTCRA T-117 EAA sediment at levels above the selected RvALs. This would be verified through a post-NTCRA sediment monitoring program. 5.2.6 Atmospheric deposition Atmospheric sources of contaminants are generally widespread (EPA 2001); contaminants are emitted to the air from both point sources (e.g., industrial facilities) and non-point sources (e.g., motor vehicles, marine vessels, trains) and may be Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 172 transported over long distances, generally in the direction of the prevailing winds. Contaminants in the atmosphere are deposited to both land and water surfaces through wet deposition (i.e., precipitation) and dry deposition (i.e., as particles). The deposition of contaminants from the air directly to a water body (e.g., the LDW) through either wet deposition or dry deposition is called direct atmospheric deposition. Although emission sources associated with oil combustion and other activities were present historically at the asphalt manufacturing facility, no sitespecific emission sources are currently active within the T-117 EAA. Indirect atmospheric deposition of contaminants occurs when contaminants deposited on upland areas are conveyed to water bodies via stormwater flow. Although not the only potential source of COCs in stormwater conveyances, contributions from atmospheric deposition can be detected through the sampling of storm solids and mitigated through the cleaning of conveyance systems and the application of other stormwater BMPs. In the LDW, the The potential contribution of contaminants via direct atmospheric deposition on the T-117 Sediment Study Area (approximately 2 ac) is relatively small compared with the potential contribution via indirect atmospheric deposition on the upland drainage areas (estimated to be approximately 12 ac, including portions of the Marina). For the most part, contaminants deposited on the T-117 upland areas become entrained in storm solids and are monitored and controlled. because of the relatively small surface areas of the T-117 Sediment Study Area (approximately 2 acres) and surrounding LDW study area (441 acres between RM 0 and RM 5) (ENSR|AECOM 2009) compared to the surface area of the Green/Duwamish Watershed (294,600 acres). Direct aAtmospheric deposition information hasdata have been collected in the vicinity of the T-117 EAA by the County (2008) and can be used to evaluate the potential contribution of contaminants to the T-117 Sediment Study Area from direct atmospheric deposition. Sixteen rounds of deposition data were collected at the South Park Community Center (SPCC) atmospheric deposition monitoring station between 2005 and 2007. The SPCC station is the closest monitoring station to the T-117 EAA and was one of five monitoring stations used by the County in their study of atmospheric deposition near the LDW. Samples collected at the SPCC station were analyzed for a number of contaminants, including phthalates, selected PAHs , and PCB Aroclors, both identified as sediment COCs for the T-117 EAA., and Data from the SPCC station were converted to atmospheric deposition flux values by the County (see Table 5-32). Fluxes calculated for other area monitoring stations were similar.16 16 Together, the SPCC, Duwamish, and Georgetown monitoring stations represent the commercial/industrial neighborhood conditions in the Duwamish Valley. For comparison, the average atmospheric deposition flux values (based only on detected results) were: 2.94 g/m2/day BEHP, 0.95 g/m2/day BBP, and 0.042 to 0.241 g/m2/day for PAHs. In all samples from these three Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 173 Table 5-32. Hypothetical contribution of COCs to T-117 Sediment Study Area based on average atmospheric deposition flux rates contribution to sediment concentrations based on atmospheric deposition flux at the SPCC station Hypothetical Contribution of Direct Atmospheric Deposition to Sediment Concentrations over a 1-Year Period by Average Sedimentation Rate Atmospheric b Sediment (mg/kg dw): Deposition Flux RvAL 2 a c COC (g/m /day) 0.1 cm/yr 0.5 cm/yr 1 cm/yr (mg/kg dw) PAHs Benzo(a)anthracene 0.048 0.015 0.003 0.001 1.7 Benzo(a)pyrene 0.074 0.023 0.005 0.002 1.5 Benzo(g,h,i)perylene 0.086 0.026 0.005 0.003 0.48 Total benzofluoranthenes 0.174 0.053 0.011 0.005 3.6 Chrysene 0.112 0.034 0.007 0.003 1.7 Dibenzo(a,h)anthracene 0.028 0.009 0.002 0.001 0.19 Indeno(1,2,3-cd)pyrene 0.051 0.002 0.003 0.002 0.53 PCBs d Total PCBs 0.011 0.003 0.00066 0.0003 0.19 a Averages were calculated using detected concentrations from only the SPCC station. b Based on calculations made using the deposition flux values provided in Column 2 and the following 3 3 assumptions: sediment transport deposition rate of 1 cm/yr; sediment density of 1.2 g/cm , or 6g/5cm (from LDW STAR); TOC content of sediment: 2%. Sample calculation for Total PCBs at a sedimentation rate of 0.5 cm/yr BEHP follows. Calculation: 2 2 (0.0112.4 g PCBsBEHP/m /day) x (365 day/yr) = 4.015876 g PCBBEHP/m/yr 2 3 (4.015876 g PCBBEHP/[m x yr]) x (1yr/0.51cm) x (100 cm/1 m) = 80387,600 g PCBBEHP/m 3 3 3 3 (80387,600 g PCBBEHP/m ) x (5 cm /6g) x (1m /1,000,000 cm) = 0.000669173 g/g PCBBEHP 0.00066973 g/g PCBBEHP = 0.00066973 ppm = 0.0006673 mg/kg PCBBEHP (dw concentration) OC normalization: (0.073 mg/kg)/(0.02 TOC) = 3.65 mg/kg OC c Sediment RvALs ias defined in Section 4. dc Represents single detected concentration of Aroclor 1254 at the SPCC station; no other samples from this station had detected concentrations of any PCB Aroclors. stations, only two PCB Aroclors were detected: Aroclor 1254 was detected in five samples at a range of 0.011 g/m2/day (detected at the SPCC station) to 0.044 g/m2/day (detected at the Georgetown station). The Beacon Hill station represents urban residential neighborhood conditions. Average atmospheric deposition flux values (based only on detected results) at this station were: 1.64 g/m2/day BEHP, 0.498 g/m2/day BBP, and 0.012 to 0.090 g/m2/day for PAHs. No PCB Aroclors were detected in any of the samples from the Beacon Hill station. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 174 BBP butyl benzyl phthalate RvAL removal action level BEHP bis(2-ethylhexyl) phthalate SPCC South Park Community Center COC contaminant of concern SQS sediment quality standard dw dry weight STAR sediment transport analysis report CSL cleanup screening level T-117 Terminal 117 OC organic carbonLDW Lower Duwamish Waterway PAH polycyclic aromatic hydrocarbon PCB polychlorinated biphenyl Hypothetical Direct Atmospheric Deposition Average Contribution to Sediment Atmospheric Concentration Over Deposition Flux 1-Year Period SQS CSL 2 a B COC (g/m /day) (mg/kg OC) (mg/kg OC) (mg/kg OC) PAHs Benzo(a)anthracene 0.048 0.073 110 270 Benzo(a)pyrene 0.074 0.113 99 210 Benzo(g,h,i)perylene 0.086 0.131 31 78 Total benzofluoranthenes 0.174 0.265 230 450 Chrysene 0.112 0.170 110 460 Dibenzo(a,h)anthracene 0.028 0.043 12 33 Indeno(1,2,3-cd)pyrene 0.051 0.078 34 88 Phthalates BEHP 2.4 3.65 47 78 BBP 1.5 2.28 4.9 64 PCBs c Total PCBs 0.011 0.017 12 65 Using conservative assumptions,17 estimated sediment concentrations for the T-117 COCs based on the average SPCC atmospheric deposition flux values were calculated 17 Conservative assumptions used to estimate sediment concentrations associated with direct atmospheric deposition: 1) all airborne contaminant mass that falls onto the LDW is sorbed to sediment, 2) sediment deposition rate of clean sediment is between 0.1 and 1 cm /yr (calculations were based on three assumed deposition rates of 0.1, 0.5, and 1 cm/year for comparison, and 3) sediment density is 1.2 g/cm3 (the lower end of the wet sediment density range reported in the LDW sediment transport analysis report (Windward and QEA 2008)). The calculation used to derive the hypothetical contributions from direct atmospheric deposition to sediment is considered to be conservative because it assumes that 100% of contaminants deposited to the LDW surface accumulate in the sediment. Atmospheric particulate matter is divided into two size classes: fine particulate matter (less than 2.5 m in diameter [PM2.5]) and coarse particulate matter (between 2.5 and 10 m in diameter [PM10]). The LDW sediment transport model showed that only 10% of sediment particles less than 10 m in size (clay or fine silt) are expected to be deposited to LDW sediment. The other 90% is transported downstream. Particulate matter deposited to the LDW via atmospheric deposition Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 175 (see Table 5-32). The hypothetical contributions from direct atmospheric deposition to sediment concentrations are all well below the SQS criteria for these chemicals and thus were less than the RvALs. These results indicate that contributions of contaminants to sediment from direct atmospheric deposition alone would not be expected to result in sediment concentrations above the RvALs. This type of conservative calculation is acceptable as a screening exercise because it places the direct atmospheric deposition pathway in context with other potential pathways and allows an estimation of the importance of this pathway relative to other pathways and relevant to source control. This type of analysis would not be used to make decisions about implementing source control measures other than to help prioritize pathways and sources for additional assessment. Based on available atmospheric deposition data and the hypothetical deposition contribution from direct atmospheric deposition, it appears that other pathways are more important for source control. The potential for recontamination through indirect atmospheric deposition is more uncertain; periodic sampling of storm solids within the T-117 conveyance systems will be conducted to assess the importance of this pathway. The calculation used to derive the hypothetical contributions from direct atmospheric deposition to sediment is considered to be conservative because it assumes that 100% of contaminants deposited to the LDW surface accumulate in the sediment. Atmospheric particulate matter is divided into two size classes: fine particulate matter (less than 2.5 m in diameter [PM2.5]) and coarse particulate matter (between 2.5 and 10 m in diameter [PM10]). The LDW sediment transport model showed that only 10% of sediment particles less than 10 m in size (clay or fine silt) are expected to be deposited to LDW sediment. The other 90% is transported downstream. Particulate matter deposited to the LDW via atmospheric deposition would be expected to have deposition rates similar to those of clay or fine silt; therefore, the use of a 100% deposition rate in the calculation is highly conservative. In addition, a sediment deposition rate of 1 cm/year is considered to be conservative because the sediment deposition rate over much of the T-117 EAA is higher than 1 cm/yr. The sediment density used in the calculations is 1.2 g/cm3, which is considered to be conservative because it at the lower end of the wet sediment density range reported in the LDW sediment transport analysis report (Windward and QEA 2008). A higher sediment density used in the calculations would generate a lower hypothetical contaminant would be expected to have deposition rates similar to those of clay or fine silt; therefore, the use of a 100% deposition rate in the calculation is highly conservative. In addition, a sediment deposition rate of 1 cm/yr is considered to be conservative because the sediment deposition rate over much of the T- 117 EAA is higher than 1 cm/yr. The sediment density used in the calculations is 1.2 g/cm3, which is considered to be conservative because it at the lower end of the wet sediment density range reported in the LDW sediment transport analysis report (Windward and QEA 2008). A higher sediment density used in the calculations would generate a lower hypothetical contaminant contribution from direct atmospheric deposition. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 176 contribution from direct atmospheric deposition.Because of the relatively small quantities of contaminants present in atmospheric deposition samples and the relatively small contribution of contaminants via direct atmospheric deposition, the potential for the direct atmospheric deposition pathway to recontaminate post-NTCRA T-117 EAA sediment is low. The potential for recontamination through indirect atmospheric deposition is more uncertain; periodic sampling of storm solids within the T-117 conveyance systems will be conducted to assess the importance of this pathway. 5.3 OVERALL SUMMARY AND MONITORING RECOMMENDATIONS All of the potential individual recontamination pathways that originate at the T--117 EAA and the RAAs (Basin Oil and Marina) have a relatively low likelihood of increasing contaminant concentrations in the post-NTCRA T-117 Sediment Study Area to concentrations above sediment RvALs. The estimated potential for recontamination is summarized in Table 5-4, and is based on the following factors: Potential contribution of contaminants to T-117 Sediment Study Area after cleanup from each ongoing source Degree of confidence in information regarding the chemical characteristics/loading from each source or the likely occurrence of an event that will impact the sediment offshore of T-117, such as a spill Table 5-4. Evaluation of post-removal recontamination risk from ongoing sources in the T-117 vicinity Potential Post- PotentialLikeli Rremoval hood to Action Impact Cause to T-117 Exceedances Sediment Study Uncertainty/ of Sediment a Source/Pathway Description Area Probability RvALs Runoff from 1.1 ac of road and+ 0.6 ac of private property (Basin Oil). Contaminated soil in ROW to be removed during the NTCRA. After Stormwater low medium low cleanup, runoff will be treated per City stormwater code (SMC 22.800) using conventional stormwater treatment technologies. Groundwater Groundwater discharge to sediment. low medium low Spills/over-water Spills that occur in the vicinity of T-117 high low low activities or from adjacent areas. Contaminated soil in T-117 upland, banks and ROW to be removed as part ab of NTCRA. RAAs with known soil Soil erosion low medium low contamination (i.e., Marina and Basin Oil) are either paved or will be remediated by others. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 177 Potential Post- PotentialLikeli Rremoval hood to Action Impact Cause to T-117 Exceedances Sediment Study Uncertainty/ of Sediment a Source/Pathway Description Area Probability RvALs Deposition from local and regional Direct atmospheric cb airshed onto the immediate area low highlow low deposition offshore of T-117. In-waterway Deposition of contaminated sediment sediment from sediment cleanup activities high low medium-low dc transport elsewhere in the waterway. Cumulative effects low medium low a Uncertainty/probability represents the confidence level in the available data. For event-driven sources (e.g., spills and in-waterway sediment), it represents the likelihood of occurrence. b Soils within the upland areas that drain to the T-117 Sediment Study Area. cb Atmospheric deposition that falls elsewhere on the drainage basin is included under stormwater. dc Cleanup activities elsewhere in the LDW will be tightly controlled to reduce the potential for contaminated materials to migrate downriver. NTCRA non-time-critical removal action RAA recontamination assessment area ROW right-of-way SMC Seattle Municipal Code T-117 Terminal 117 Each of these factors is qualitatively rated high, medium, or low. These two factors are then combined to evaluate the overall potential for an individual source to cause recontamination. Spills and the transport of contaminated sediment from cleanup activities elsewhere in the LDW have an overall rating of low and medium-low, respectively, because of the high potential for impacts, but both have a low probability of occurrence. For example, the likelihood of a major spill occurring immediately adjacent to T-117 is fairly low; similarly, the chance of recontamination from upriver cleanup activities is not expected to be highlow because these cleanups will be tightly controlled to minimize the potential for offsite migration of contaminants. Groundwater discharges and atmospheric deposition also received medium and low rankings, respectively. Information regarding atmospheric loading (Section 5.2.6) as well as groundwater in the proximity of the shoreline is available. The quality of groundwater that discharges from the T-117 Uupland Study Area and Aadjacent Sstreets is expected to improve, primarily as a result of the removal of contaminated soil located above or in contact with the shallow aquifer. Although little is currently known regarding groundwater beneath the Adjacent Streets, additional pre-design groundwater monitoring will be conducted (Section 9.5) to verify that this groundwater will not be a future source of recontamination to the post-NTCRA T-117 EAA. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 178 Additional groundwater monitoring is also planned to further assess the potential for groundwater from the Marina and Basin Oil properties to contribute to recontamination. It is recognized that the data necessary to assess some of the pathways (e.g., dioxin and furan groundwater data) are limited. These additional information needs will be addressed through the implementation of measures set forth in Section 9.4. Stormwater discharges and soil erosion are rated low because stormwater will be treated prior to discharge, which will remove the majority of the solids; and most of the contaminated soil within the area that drain to T-117 will be removed as part of the NTCRA. Contaminated soil that remains at the Marina and the Basin Oil properties are also not expected to pose a risk for sediment recontamination. The Marina was evaluated by Ecology (SAIC 2009), and results of the quantitative recontamination assessment showed that eroded soil from the Marina would be unlikely to impact the adjacent T-117 Sediment Study Area. Contaminants in Basin Oil soil will be addressed through actions by others and overseen by Ecology, ensuring that any remaining soil is not subject to erosion and transport at this site.- Potential recontamination from transport and deposition of contaminated sediment from other portions of the LDW has not been addressed. As discussed in Section 5.2.4, it is inappropriate to apply the LDW STM to the T-117 Sediment Study Area. The design phase of the NTCRA will include the design of post-NTCRA stormwater, groundwater, and sediment monitoring programs to verify that recontamination of post-NTCRA T-117 Sediment Study Area does not occur. If it appears that post- NTCRA contaminant concentrations are increasing, a variety of potential recontamination sources and pathways will be evaluated, such as, but not limited to: Ongoing source control actions in the Adjacent Streets and Residential Yards Study Area Further evaluation of sources and source pathways from the RAAs (the Marina and Basin Oil) Review of groundwater monitoring results for indications of increased COC concentrations Investigation of atmospheric deposition and entrainment in stormwater SPU will sample solids in the storm drain system and stormwater in the portion of the Adjacent Streets and Residential Yards that will discharge at or in the vicinity of T--117 as required by EPA to evaluate whether the removal action and proposed stormwater treatment system are effective in controlling PCBs and other LDW COCs in the runoff from this area. An adaptive management strategy will be developed and will phase in increasingly more aggressive source investigations and, if necessary, an evaluation of Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 179 additional treatment until the source(s) of any future contamination is identified and controlled. Further analysis of airborne particulate loads within the vicinity of the T-117 EAA may also be necessary in order to further assess inputs from the atmosphere if elevated COCs are noted in stormwater solids following the implementation of the NTCRA. Additional source control measures in the vicinity of the T-117 EAA, such as the completion of the soil cleanup at Basin Oil, are advised to further minimize the potential for recontamination. Other ongoing LDW-wide source control actions and information collected by the LDW SCWG member agencies (e.g., SPU stormwater solids data) will be regularly reviewed as a means of evaluating potential sources in the T-117 EAA vicinity. This review will occur annually or whenever the LDW Source Control Work Group publishes an updated source control status report. The post- NTCRA groundwater monitoring will also be a key element in the evaluation of the potential for post-NTCRA recontamination of the T-117 sediment. Finally, the timing and sequencing of in-water LDW cleanups projects (e.g., Boeing Plant 2, Slip 4, South Park Bridge removal, and the LDW) should be considered. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 180 6 Identification, Evaluation, and Screening of Technologies This section of the EE/CA considers removal, treatment and disposal technologies that are suited for implementing the removal action at the T-117 EAA. The cleanup activities described in this EE/CA focus on sediment and soil removal, so emphasis is placed upon those technologies that are applicable to those media, are readily available, and can be implemented within the anticipated NTCRA timeframe. This section: Identifies and provides an evaluation and screening of soil removal technologies (i.e., excavation) Identifies and provides an evaluation and screening of sediment dredging and capping technologies Identifies, discusses, and evaluates treatment and disposal options The identification and evaluation of technologies (USACE 2003) takes into account a broad range of methods, such as the use of multi-user disposal sites that have been identified by LDWG in Identification of Candidate Technologies for the Lower Duwamish Waterway (RETEC 2005), hereafter referred to as the Candidate Technologies Report. This report was designed to help ensure compatibility with remedial technologies that may eventually be applied within the LDW as a whole. The technologies identified in this section of the EE/CA are used to develop the removal action alternatives presented in Section 7. These alternatives must be applicable to all the removal areas within the T-117 EAA as identified in Section 4, including the T-117 Sediment Study Area, T-117 Upland Study Area, and the Adjacent Streets and Residential Yards Study Area. Thus, technologies that address submerged and intertidal sediment as well as upland soil must be included. Removal actions to address the shoreline and sediment will use a variety of technologies. Figure 6-1 presents the various shoreline and sediment zones that are described throughout the rest of this document. In addition to the primary removal technology, all alternatives must include supporting methods needed to prepare the site for the selected removal action and support the removal activities (e.g., aboveground structural demolition, asphalt removal, well abandonment, and implementation of site security measures). Soil/sediment staging areas and water management systems (for surface water and groundwater) and other support facilities will also be necessary. A discussion of these supporting methods is included in the description of each alternative (Section 7). Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 181 Slipsheet for 8.5 x 11 Figure 6-1. Locations of zones within the shoreline and sediment Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 182 The evaluation and selection of technologies in this EE/CA emphasizes those technologies demonstrated to be proven and readily implemented at full scale (rather than research or pilot-scale). An additional key selection criterion includes the appropriateness of the technology for the size and site-specific conditions of the T-117 EAA, as well as the time frame of the NTCRA. Sediment remediation technologies that were screened and eliminated in the Candidate Technologies Report (RETEC 2005) for application in the LDW were not included in this screening. General technologies discussed in this section for the T-117 NTCRA include those associated with: Removal and containment Treatment or disposal Monitored natural recovery and enhanced natural recovery are not considered to be applicable strategies for the T-117 EAA because of the elevated concentrations and persistent nature of contaminants located in the T-117 EAA Upland and the Adjacent Streets and Residential Yards Study Areas and the uncertainty regarding low sedimentation rates estimated for portions of the T-117 Sediment Study Area (Windward and QEA 2005) within the T-117 Sediment Study Area. Some types of institutional controls may be implemented, as necessary, to help ensure the long-term maintenance and integrity of remediated upland areas and sediment caps, but institutional controls are not considered to be a substitute for active removal measures and are not appropriate or sufficiently protective for use at the T-117 EAA if used as the sole measure for preventing exposure to contaminants. Institutional controls were not considered for areas where their use would preclude achieving RAOs. Restrictive covenants may be appropriate in areas where sediment capping is used to meet sediment RAOs as part of a removal alternative or as a component of future redevelopment (i.e., construction of upland or intertidal habitat) in order to prohibit activities that would compromise a cap and potentially release contaminated materials that remain beneath the cap. However, such controls may be limited and cannot be used where they might be infeasible (e.g., where they would interfere with tribal use of the area or could not be effectively implemented or enforced). 6.1 SOIL AND SEDIMENT REMOVAL AND CONTAINMENT TECHNOLOGIES A comprehensive list of potential removal technologies was compiled, reviewed, and screened against specific criteria (Appendix K); a summary of this evaluation is presented as Table 6-1. Applicable technologies for the T-117 EAA include those well-known, proven technologies that can be used for soil and sediment removal (i.e., excavation and dredging). Land-based removal technologies are used as a means of excavating contaminated soil and nearshore intertidal sediment using equipment positioned on land. Over-water removal technologies include dredging as a means for removing offshore subtidal sediment. These technologies are effective when used in Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 183 conjunction with procedures and safeguards to limit uncontrolled release of soils and sediment or excessive turbidity in the LDW during the removal action. 6.1.1 Land-based technologies The primary land-based removal technology under consideration for the T-117 EAA is excavation. Excavation has already been used as the principal means of removing soil in the T-117 Upland Study Area (RETEC 2007b) and the Adjacent Streets (Integral 2006a) and is also a viable method for addressing the cleanup of nearshore sediment. Excavation is typically conducted using backhoes, front-end loaders, and dump trucks. Supporting methods include shoring (for excavations that are deep or close to structures), soil stockpiling and containment, dust control, groundwater extraction (for dewatering deeper excavations), and storing and treating extracted groundwater. Contaminated soil or sediment can be excavated, placed in lined trucks, and transported to appropriate treatment or disposal facilities. Truck wheel washing and inspection are necessary to control soil track-out during excavation work. Excavation and its supporting methods have been successfully implemented during previous removal actions and are proven removal methods for this site; they have thus been retained for inclusion in removal action alternatives. Land-based containment technologies (e.g., capping) that require institutional controls have not been retained for application in the T-117 Upland or Adjacent Streets and Residential Yards Study Areas have not been retained because they are inconsistent with the RAO (Section 4.4) of allowing for a range of possible land uses in these study areas. One exception is the use of clean cover (soil) that would be placed onto cleaned upland areas as needed for the construction of habitat. As specified in WAC-173-340- 7492(3), an institutional control may be required to ensure that site conditions within developed habitat areas are maintained and the exposure of species to unacceptable soil contaminants is prevented. 6.1.2 Over-water technologies This section discusses over-water technologies for addressing contaminated sediment at the T-117 Sediment Study Area, which are dredging and capping. Both technologies have been applied elsewhere within the LDW and have been proven to be feasible methods for removing or containing contaminated sediment. 6.1.2.1 Sediment dredging As mentioned previously, land-based excavation may also be used as a means for removing contaminated sediment from the intertidal mudflat. This approach could be implemented without generating excessive turbidity in the water column because excavation would be conducted "in the dry" during low tides (this process is discussed in more detail in Section 7.1.1.4). Only the remaining less-contaminated Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 184 subtidal sediment would need to be removed using conventional over-water dredging methods. For subtidal sediment, both mechanical and hydraulic dredging are candidate technologies. Mechanical dredging involves lowering a bucket or clamshell to the bottom of the river, excavating the target material, and then lifting the bucket to the surface. The dredged material is placed onto a barge for transport to an offloading site. Environmental bucket dredges are equipped with specially designed buckets to reduce the outflow of contaminated solids during the dredging process. The hydraulic dredging process involves using agitation equipment to loosen the target material from the river bed and then mixing the loosened material with water to form slurry. A centrifugal pump is used to convey the slurry through a hose or pipeline to a handling site. Hydraulic dredges for low-volume environmental remediation can range from small (4-to-6-in.-diameter discharge) diver-guided suction dredges used for working in and around confined areas to floating cutterhead hydraulic dredges (8-to-16-in.-diameter discharge) for working in less unrestricted areas. Hydraulic dredging would require the development of a large handling site nearby to dewater the dredge spoils. The resulting solids would then need to be transported to a disposal facility. For the T-117 site, several factors would limit the effectiveness of hydraulic dredging for sediment remediation, such as: Spillage The cutterhead or auger action associated with hydraulic dredging would leave a spillage layer of sediment not captured by the dredge. Spillage layers are composed of a mixture of sediment from the cut face of the dredged area that is not captured by the hydraulic dredge, with chemical concentrations similar to the average concentration of the chemical in the dredged material. As a rule of thumb, the thickness of spillage layer is on the order of half of the discharge pipe diameter (Palermo et al. 2008). So a 12-in. dredge (12-in.- diameter discharge pipe) would leave a spillage layer of approximately 6 in. thick. Slurry Hydraulic dredging generates a slurry that is on the order of 10 parts water to 1 part sediment. Small hydraulic dredges can generate larger volumes of water because of the constraints of small working areas. Consequently, hydraulic dredging requires the mobilization, construction, and operation of a handling site to manage the slurry generated by a hydraulic dredge, which is typically only cost effective for long-duration projects or for work that can only be completed by hydraulic dredging, such as diver dredging around constrained areas. For example, the remediation of the Thea Foss Waterway in Commencement Bay used hydraulic dredging because the slurry could be pumped into a 10- ac placement site (former St. Paul Waterway), which was large enough to clarify the slurry before discharge to Commencement Bay. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 185 Debris The type of debris commonly found in the T-117 intertidal mudflat, such as riprap and rock from the shoreline and small wood debris from the river, area would likely plug and damage the smaller-sized dredges (6- to 14- in.-diameter discharge pipe) typically used for environmental remediation of this scope. Because of these factors (i.e., spillage, slurry, debris) and the relatively small volume of material to be dredged, hydraulic dredging was not considered practical for this removal action. Mechanical dredging is therefore the preferred technology for subtidal sediment removal. The specific type of dredging bucket will be selected based on water quality performance criteria established during the design phase of the NTCRA. 6.1.2.2 Sediment capping Sediment capping could be completed using either land-based earth-moving equipment (e.g., backhoes or other types of excavators, front-end loaders, dump trucks, conveyor systems) or conventional offshore floating equipment. Clean capping material could be imported to the site in dump trucks or on barges and then placed as engineered fill. The cap would be designed to resist disturbance and the re-exposure of materials contained beneath the cap. The three primary functions of capping are (Palermo et al. 1998): Physical isolation of the contaminated sediment from human and ecological receptors Stabilization of contaminated sediment and the prevention of resuspension and transport to other sites Reduction of the flux of dissolved contaminants into the water column. The cap would be specifically designed to provide these functions in a manner that is compatible with the site conditions along the T-117 shoreline, including sediment grain size, bathymetry, surface water flow, and ship traffic. Capping designs prepared in accordance with USACE guidance for PCB- contaminated sediments in river settings can have caps that range from 12 to 36 in. thick. The caps are often multilayered to provide chemical isolation immediately over the impacted sediment and include a sand and gravel/cobbles layer to prevent erosion from waves and prop wash and a surficial habitat layer of sand and gravel. A robust 3-ft- thick cap configuration is being assumed for the EE/CA (portions of the cap could be even thicker, if needed, to accommodate clamming). It consists ofA typical cap design includes three layers: a sandy material to provide primary physical and chemical containment of the underlying sediment, an armored layer (cobbles) to protect against erosion, and a surface layer of natural sand and gravel. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 186 Sediment capping could also be completed using floating equipment similar to that used for mechanical dredging. The dredge bucket would be used to collect capping material from a haul barge and place the material on the bed of the waterway. A typical cap design includes three layers: a sandy material to provide primary physical and chemical containment of the underlying sediment, an armored layer to protect against erosion, and a surface layer of natural sand and gravel. If necessary, Tthe specific cap design and structural components will would be further evaluated and incorporated during the design phase of the NTCRA. Cap thicknesses and composition will would be based on guidance published by EPA and USACE guidance (Palermo et al. 1998; EPA 2005d). Sediment capping has been retained as a technology for inclusion in one or more of the removal action alternatives to be presented in Section 7. 6.2 MATERIAL TREATMENT AND DISPOSAL This section describes the broad range of soil and sediment treatment and disposal technologies identified and evaluated for the T-117 EAA. A comprehensive list of potential treatment and disposal technologies was compiled, reviewed, and screened against specific criteria (Appendix K). The Candidate Technologies Report (RETEC 2005) prepared for the LDW FS serves as a basis for identifying applicable technologies. However, because the Candidate Technologies Report focused on sediment treatment technologies, this EE/CA also includes consideration of a full range of soil treatment technologies. Additional sources of information on technologies included: Federal Remediation Technologies Roundtable. Treatment technologies screening matrix for SVOCs (Platinum International 2002, Sections 4.1 through 4.8) Superfund Guidance on Remedial Actions for Superfund Sites with PCB Contamination (EPA 1990) Engineering Issue: Technology Alternatives for the Remediation of PCB-Contaminated Soil and Sediment (Davila et al. 1993), prepared for EPA Application, Performance, and Costs of Biotreatment Technologies for Contaminated Soils (Battelle 2002), prepared for EPA Commercially permitted PCB disposal facilities (EPA 2008a) Table 6-1 includes a list of the identified treatment and disposal technologies and information regarding the technology evaluation and screening process. Each technology was evaluated for its applicability to the T-117 NTCRA. The evaluation addressed expected soil and sediment quantities and physical characteristics, estimated COC concentrations, processing costs, and the availability of suitable staging and transfer areas for storing, treating, and loading excavated or dredged Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 187 materials. Technologies were evaluated and selected based on their estimated implementability, effectiveness, and cost. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 188 Table 6-1. Review of can Review of candidate removal action technologies for the T--117 NTCRA Contaminants of Concern Process Option Description Typically Treated Screening Decision In Situ Treatment Biological Not applicable: not feasible for PCBDegradation of organic contaminants in the soil using contaminated soils, site hydrologic Effective principally to PAHs, other non- Aerobic microbes in the presence of oxygen. Enhanced characteristics of the fill (potential halogenated SVOCs, and BTEX. Biodegradation biodegradation bioremediation includes the injection of nutrients, preferential flow pathways) not of PCBs not feasible. oxygen or other amendments. conducive to treatment. Too much treatment time would be required. Not applicable: not effective for PCB The injection of a methanogenic culture, anaerobic contaminated soils, site hydrologic Anaerobic mineral medium and routine supplements of glucose to Effective principally on chlorinated VOCs. Bio- characteristics of the fill (potential biodegradation maintain methanogenic activity. Nutrients and pH are degradation of PCBs is not proven. preferential flow pathways) not controlled to enhance degradation. conducive to treatment; treatment time constraints. Used to address metals, pesticides, solvents, explosives, crude oil, PAHs, and landfill Not applicable: not proven to clean up A process that uses plants to remove, transfer, leachate. Effective at up-taking PCBs in shallow Phyto-remediation PCBs to site RvALs, unable to stabilize, and destroy contaminants in soil. soils (surface to 3 ft depths) and low remediate to necessary depth. concentrations, but not proven to meet RvALs for higher concentrations of PCBs. Chemical Delivery of oxidizers into soils using injection wells in Not applicable: not effective for PCB Used to treat VOCs. Oxidation is less efficient contaminated soils. Oxidation of organics using contaminated soils, for site soil Chemical oxidation with SVOCs including pesticides, PAHs, and oxidizing agents such as ozone, peroxide, characteristics and may pose additional PCBs. permanganate, or Fenton's reagent. site risks. Physical-Extractive Processes Vacuum is applied to the vadose zone soil to induce the Not applicable: not appropriate PCBs in Soil vapor Effective at extracting VOCs. Not effective at controlled flow of air and remove VOCs and some contaminated soils due to extremely low extraction extracting PCBs. SVOCs. vapor pressure. Water or water containing an additive to enhance Not applicable: Unproven technology, contaminant solubility is applied to the soil or injected The technology can be used to treat VOCs, possible contaminant migration to Soil flushing into the groundwater to raise the water table into the SVOCs, fuels, and pesticides. Technology surface waters and heterogeneous fill contaminated soil zone. Contaminants are leached into unproven to treat PCBs to 1 mg/kg. soils. PCBs are strongly adsorbed onto the groundwater, which is extracted and treated. soil particles. Table 6-1. Review of candidate removal action technologies for the T-117 NTCRA (cont.) Contaminants of Concern Process Option Description Typically Treated Screening Decision Cracks are developed by fracturing beneath the surface in low permeability soils to open new passageways that Used on a variety of COCs, depending on the in- Not applicable: Some site soils have Fracturing increase the effectiveness of many in-situ processes situ process it is used in conjunction with. high permeability. and enhance extraction efficiencies. Not applicable: Site properties such as debris (e.g., USTs, remnant Steam injection, hot air injection, electrical resistance underground asphalt manufacturing Applicable primarily to VOCs, also used for heating, electromagnetic heating, fiber optic heating, or facility structures, foundations, rip rap, Thermal treatment SVOCs, pesticides and fuels. Less effective for radio frequency heating is used to increase the pilings) make effective application PCBs. volatilization rate of SVOCs and facilitate extraction. infeasible, Not applicable to PCB contaminated soils, lack of full scale demonstration. Removes metals and polar organic contaminants from Not applicable: Technology is not low permeability soil, mud, sludge, and marine dredging Electro kinetic Typically used for heavy metals, anions, and applicable to PCB & TPH contaminated through the application of a low intensity direct current separation polar organics. Limited applicability to PCBs. soils, or to highly permeable soils and between ceramic electrodes that are divided into a buried debris. cathode array and an anode array. Physical Immobilization Not applicable to PCB contaminated Traps or immobilizes hazardous substances using Generally used for inorganics, solidification for soils and contamination is below the Soil solidification physical or chemical means. organics is not a proven technology. water table, heterogeneous soils, and leaching potential of solidified soils. Not applicable: remediation of PCB contaminated soils to 1 mg/kg is Uses an electric current in situ to melt sediment or other unproven. Additional challenges include earthen materials at extremely high temperatures Applicable to inorganic and organic chemicals. heterogeneous soils, buried debris, and Vitrification (2,900-3,650 F). Inorganic compounds are Has been tested on PCBs, but not at a full scale dewatering of saturated soils. Risks incorporated into the vitrified glass and crystalline mass and at action levels of 1 mg/kg. include possibility of generating dioxins and organic pollutants are destroyed. and furans as by-products due to high treatment temperatures. Ex Situ Treatment Biological Excavated soils are mixed with amendments and Not applicable to PCBs. Biopile treatment has placed in aerated aboveground enclosures. Moisture, Not applicable: Not a technology that is Biopiles been applied to treatment of non-halogenated heat, nutrients, oxygen, and pH can be controlled to applied to PCB contaminated soils. VOCs and fuel hydrocarbons. enhance biodegradation. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 190 Table 6-1. Review of candidate removal action technologies for the T-117 NTCRA (cont.) Contaminants of Concern Process Option Description Typically Treated Screening Decision Soil is mixed with amendments and placed on a treatment area that typically includes leachate Not applicable to PCBs. Contaminants that have collection. The soil and amendments are mixed using been successfully treated using land farming Not applicable: Degradation rates not in Land farming/ conventional tilling equipment or other means to include diesel fuel, No. 2 and No. 6 fuel oils, JP- keeping with NTCRA objectives. composting provide aeration. Moisture, heat, nutrients, oxygen, and 5, oily sludge, wood-preserving wastes Requires long processing time and large pH can be controlled to enhance biodegradation. Other (pentachlorophenol and creosote), coke wastes, processing area. organic amendments such as wood chips, potato and certain pesticides. waste, or alfalfa are added to composting systems. Fungal biodegradation refers to the degradation of a Bench scale studies indicate a destruction of Not applicable: Limited full scale Fungal wide variety of organic pollutants by using fungal lignin- PCBs between 29 and 70%. Limited full scale experience and limited applicability to biodegradation degrading or wood-rotting enzyme systems (example: application data. PCBs. white rot fungus). Techniques have been successfully used to An aqueous slurry is created by combining soil with remediate soils, sludges, and sediments water and other additives. The slurry is mixed to keep contaminated by explosives, petroleum Not applicable: technology for solids suspended and microorganisms in contact with hydrocarbons, petrochemicals, solvents, Slurry-phase remediation of PCBs is still developing, the contaminants. Upon completion of the process, the pesticides, wood preservatives, and other biological treatment and low throughput of available slurry is dewatered and the treated soil is removed for organic chemicals. Effective on PCBs when a equipment. disposal. Sequential anaerobic/aerobic slurry-phase sequential anaerobic/aerobic slurry-phase bioreactors are used to treat PCBs. bioreactor is used, but limited in full scale demonstrations. Chemical Reduction/oxidation chemically converts hazardous Reduction/ oxidation is effective for inorganics contaminants to nonhazardous or less toxic compounds Reduction/ and is less effective for SVOCs such as PCBs or Not applicable to PCB and TPH that are more stable, less mobile, and/or inert. The oxidation soils with high levels of oil and grease; not contaminated soils. oxidizing agents most commonly used are applicable to the site COCs. hypochlorites, chlorine, and chlorine dioxide. Contaminated soils and the reagent (typically potassium polyethylene glycol) are mixed and heated in Not applicable due to infrastructure Dehalogenation a treatment vessel. The reaction causes the Applicable to treating PCBs. requirements and reagent and process polyethylene glycol to replace halogen molecules and wastes. render the compound nonhazardous or less toxic. Contaminated soil and solvent extractant are mixed in an extractor, dissolving the contaminants. The Effective in treating soils containing primarily extracted solution is then placed in a separator, where Not applicable: due to infrastructure Solvent extraction organic contaminants such as PCBs, petroleum the contaminants and extractant are separated for needs, and fate of solvents in soil. wastes, and VOCs. treatment and further use (example: B.E.S.T. and propane extraction process). Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 191 Table 6-1. Review of candidate removal action technologies for the T-117 NTCRA (cont.) Contaminants of Concern Process Option Description Typically Treated Screening Decision Multi-step process of preprocessing, aeration, sediment Not applicable: unproven technology, Soil washing Applicable to treating PCBs, but unproven at full washing, cavitation and oxidation and liquid/solid time for permitting, and necessary (biogenesis) scale to meet RvALs. separation. infrastructure. Physical Not applicable: does not destroy Applicable to SVOCs, fuels, inorganics, and Contaminated fractions of solids are concentrated contaminants; must be used in selected VOCs and pesticides. Only applicable Separation through gravity, magnetic or sieving separation conjunction with other technologies; to adsorptive COCs that would adhere to the processes. slow throughh put; and extensive fine-grained soil. infrastructure necessary. Ultraviolet energy in sunlight destroys contaminants Limited information on destruction efficiency of Not applicable: unproven technology in Solar detoxification through photochemical and thermal reactions. PCBs at previous site applications. large scale application. The mobility of constituents in a solid medium is Not applicable: slow through put of Primarily used for inorganics; vitrification is Solidification/ reduced through addition of immobilization additives. available equipment, unpredictable effective for organics. Not proven to meet action vitrification Various additives and processes are available for leaching characteristics of solidified levels at full scale implementation of PCBs. different COCs. PCB contaminated soils. Thermal Temperatures greater than 1,400 F are used to Applicable to site COCs where concentrations volatilize and combust organic chemicals. Commercial exceed the hazardous waste designation; Not applicable: due to expense and time Onsite incineration incinerator designs are rotary kilns equipped with an principally PCBs > 50 50 mg/kg. Would also be of PSCAA new source permits. afterburner, a quench, and an air pollution control effective at destruction of petroleum waste system. Temperatures in the range of 200 to 600 F are used to Low-temperature volatilize and combust organic chemicals. These Used to treat non-halogenated VOCs and fuels Not applicable: Not effectively applied to thermal desorption thermal units are typically equipped with an afterburner and SVOCs at reduced effectiveness. PCB contaminated soils. and baghouse for treatment of air emissions. Applicable to SVOCs, PAHs, PCBs, pesticides, volatile metals, VOCs. Limited full scale demonstrability for PCBs. The process is Not applicable: does not destroy Temperatures in the range of 600 to 1,200 F are used applicable for the separation of organics from High-temperature contaminants; must be used in to volatilize organic chemicals. These thermal units are refinery wastes, coal tar wastes, wood-treating thermal desorption conjunction with other technologies; typically equipped with an afterburner and baghouse for wastes, creosote-contaminated soils, then destruction slow throughput; and extensive destruction of air emissions. hydrocarbon-contaminated soils, mixed infrastructure necessary. (radioactive and hazardous) wastes, synthetic rubber processing waste, pesticides and paint wastes. Chemical decomposition is induced in organic materials Not applicable: due to requiring specific by heat in the absence of oxygen. Organic materials The target contaminant groups are SVOCs and feed size and materials handling Pyrolysis are transformed into gaseous components and a solid pesticides requirements, and dewatering of soil. residue (coke) containing fixed carbon and ash. Does not destroy metals. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 192 Table 6-1. Review of candidate removal action technologies for the T-117 NTCRA (cont.) Contaminants of Concern Process Option Description Typically Treated Screening Decision Offs-Site Commercial Disposal Containment Off-site disposal at a licensed commercial landfill facility Applicable to site COCs below hazardous waste Applicable: feasible for soils with PCB Subtitle D landfill that can accept nonhazardous soil (PCB < 50 mg/kg). designations (PCB<50 mg/kg). concentrations < 50 mg/kg. Off-site disposal at a licensed commercial landfill facility Applicable to site COCs exceeding hazardous Applicable: feasible for soils with PCB Subtitle C landfill that can accept hazardous soil removed by excavation waste designations (PCB > 50 50 mg/kg). concentrations > 50 50 mg/kg. (PCBs >50 50 mg/kg). Physical Applicable to SVOCs, fuels, inorganics, and Contaminated fractions of solids are concentrated Not applicable: commercial permitted select VOCs and pesticides. Only applicable to Separation through gravity, magnetic or sieving separation disposersal facilities not available in the adsorptive COCs that would adhere to the fineprocesses. region. grained soil. Thermal Offsite incineration and disposal at a licensed commercial facility that can accept hazardous soil Applicable to site COCs where concentrations Alternate thermal Applicable: appropriate for Toxic removed by excavation (PCB > 50 50 mg/kg). exceed the hazardous waste designation; destruction or Substances Control Act (TSCA; PCBs Depends on analytical data from excavated soil. principally PCBs > 50 50 mg/kg. Would also be incineration >50 50 mg/kg) material. Dewatering may be required to reduce water content for effective at destruction of petroleum waste. transportation. Chemical Contaminated soils and the reagent (typically potassium polyethylene glycol) are mixed and heated in Not applicable: commercial permitted Dehalogenation a treatment vessel. The reaction causes the Applicable to treating the site COCs. disposers disposal facilities not available polyethylene glycol to replace halogen molecules and in the region. render the compound nonhazardous or less toxic. BTEX benzene, toluene, ethylbenzene, and xylene PCB polychlorinated biphenyl TPH total petroleum hydrocarbon COC contaminant of concern PSCAA Puget Sound Clean Air Agency TSCA Toxic Substances Control Act cy cubic yards RvALs removal action levels VOC volatile organic compound FRTR Federal Remediation Technologies Roundtable SVOC semivolatile organic compound PAH polycyclic aromatic hydrocarbon T-117 Terminal 117 Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 193 As presented in Table 6-1, both in situ and ex situ treatment technologies were identified and evaluated. In situ treatment technologies were not retained because of a variety of implementability and effectiveness limitations, including the following: NoAllMany treatment technologies would likely not meet the RvALs specified for the site or are not applicable because of performance and processing limitations. For example, there is a lack of performance data for in situ biodegradation, the site contamination at the T-117 EAA is not limited to the surface so phytoremediation would not be effective, and site soil includes heterogeneous fill and debris, which would be difficult to process using soil flushing, vitrification, or thermal treatment. Treatment timeframes would be unacceptably long as compared with those for excavation and would result in a protracted implementation period not in keeping with the concept of an early action (i.e., there would be a much higher likelihood that the NTCRA would not be completed prior to the implementation of remedial action[s] for the LDW). Possible discharges to the LDW during treatment (e.g., chemicals associated with oxidation, soil flushing, and solidification) could pose an unacceptable risk to LDW sediment, and water quality and would need to be managed. These chemicals include oxidants, such as permanganate, or surfactants that supersaturate contaminants in water; these chemicals would be present at high concentrations and would pose a more significant risk to water quality than is currently posed by site COCs. Ex situ treatment technologies were eliminated because of a variety of implementability and effectiveness limitations, including the following: Treatment technologies cannot be performed onsite because most available land within the T-117 EAA will be subject to excavation during removal action implementation. The largest area within the T-117 Upland Study Area not expected to be excavated is less than 0.10 ac is size; this area is much smaller than the area that would be needed for any ex situ treatment system. Treatment would not likely achieve RvALs at or below those established for the T-117 EAA, particularly levels sufficient to meet a broad range of possible future land uses (including terrestrial habitat criteria), and offsite disposal would still be required. RvALs are difficult to achieve because the mixture of organic and inorganic COCs and the persistent nature of the organic COCs make it difficult to effectively treat the soil. The longer timeframe required to process large volumes of soil could delay completion of the NTCRA. For example, a typical mobile thermal treatment unit would require two to three dry seasons of operation (i.e., years) to treat all of the excavated soil. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 194 EPA-permitted aAlternative PCB treatment technologiestechnologies would pose unacceptable constraints on the project, including prolonged timeframes to demonstrate the site-specific efficiency and reliability (e.g., the possible need for pilot or demonstration testing), low probability of institutional acceptance, and performance uncertainties relative to disposal methods specifically approved under TSCA for PCBs. Preferred disposal options for both soil and sediment would be at Subtitle C (TSCA) and Subtitle D landfills. The conclusion that commercial landfill disposal is a cost- -effective and environmentally acceptable solution is consistent with the findings of the Puget Sound Confined Disposal Site Study (USACE 2003), which was co-sponsored by Ecology, WDNR, and the Puget Sound Water Quality Action team with cooperation from EPA Region 10, US Fish and Wildlife Service (USFWS), and Washington Public Ports Association. Although there are several alternative technology treatment facilities that are permitted by EPA, these facilities are not located within a reasonable distance from T-117 and are not cost competitive with Subtitle C or D disposal. The closest applicable facilities that have an incinerator and a low-temperature thermal desorption unit, are both located near Salt Lake City, Utah. With disposal, soil would be hauled approximately 5 miles and loaded onto trains for transport to a commercial landfill. Thus, commercial alternative technology treatment technologies facilities were not retained. 6.3 SUMMARY OF RETAINED TECHNOLOGIES Table 6-2 presents a summary of technologies retained for inclusion in one or more of the removal action alternatives discussed in Section 7. Table 6-2. Retained Rremoval action technologies retained for the T-117 NTCRAEAA Technology/ Category Method Applicable Media Notes land-based upland soil; Technology is appropriate and readily available for the excavation nearshore sediment scale and site-specific conditions at the T-117 EAA. Removal Technology is proven and available within the project over-water area. Special bucket designs and operating procedures mechanical sediment can be used for mechanical dredging to limit release of dredging solids. Technology is appropriate for the T-117 Sediment Study Area, but will would likely require restrictive covenants on property use to prohibit activities that could disturb the cap, and long-term monitoring of additional analysis of Containment in-water cap sediment COCs and cap thickness monitoring would be necessary to demonstrate that the cap remains in place and provides the intended isolation of impacted sediment. effectiveness. Capping must consider post-placement hydraulic conditions.. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 195 Technology/ Category Method Applicable Media Notes Method is available and typically used for managing hazardous or dangerous materials, including soil withthat TSCA-designated require special landfill design and operation because Subtitle C landfill waste soil or PCB concentrations that exceed TSCA-specified limits disposal sediment (i.e., equal to or greater than 50 mg/kg). Applicable predominately predominantly to soil and some Disposal nearshore/bank sediment. Method is available and typically used for managing non-hazardous or materials that are not designated as hazardous or Subtitle D landfill non-dangerous soil dangerous wastes. Applicable to sediment, soils in the disposal or sediment Adjacent Streets and Residential Yards soil Study Area, and some T-117 Upland Area Study Area soil. COC contaminant of concern PCB polychlorinated biphenyl EAA early action area T-117 Terminal 117 na not applicable TSCA Toxic Substances Control Act Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 196 7 Removal Action Alternatives This section presents the two removal action alternatives identified for the T-117 EAA and describes the No Action alternative, which was developed to provide a basis for the comparative evaluation of alternatives (Section 8). In particular, this section: Discusses how each alternative would be applied to the T-117 EAA Discusses the implementability, effectiveness, and estimated cost of each alternative Presents project completion options The two removal action alternatives incorporate the technologies evaluated and retained in Section 6 and address the removal of contaminated soil in the T-117 Upland and Adjacent Street and Residential Yards Study Areas and the removal or capping of sediment in the T-117 Sediment Study Area. Because the selected action levels for the upland portion of the site are low enough to provide for a broad range of future land uses (including the need to achieve RvALs sufficient for possible habitat redevelopment in the T-117 Upland Study Area), this EE/CA does not include alternatives that are solely based on current upland land use. Such alternatives might have been considered for the T-117 EAA if the final site use were to be limited to industrial or restricted-access facilities. However, RvALs based on industrial or restricted-access exposure assumptions are not appropriate for the T-117 EAA because of the EPA mandate for unrestricted land use (EPA 2007b), which was based on the T-117 EAA's proximity to residential areas and the LDW shoreline, the site RAOs, and MTCA. The two alternatives retained in this EE/CA represent the "maximum feasible" removal action in terms of the extent and level of site cleanup, rather than a mid-range of options as might otherwise be considered given a more limited future site use and a different set of removal action goals and objectives. . A range of treatment and disposal technologies for removal of soil and sediment were evaluated in Section 6, and used to assemble two removal alternatives as well as the one technology (i.e., offsite disposal) was retained. The two retained alternatives, as well as the No Action alternative, which are summarized below and in Table 7-1 and the following bullets. No Action alternative The No Action alternative has been retained only to provide a basis for comparing the overall effectiveness of the two identified removal alternatives (i.e., Alternatives 1 and 2). The No Action alternative is not a viable removal action alternative and does not meet the requirement to consider a broad range of possible future land uses or potential habitat development goals for this project. Under the No Action Alternative, no activities would be implemented to remove, contain, or treat contaminated Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 197 upland soil or intertidal and subtidal sediment within the EAA. The site would remain in its current condition with ongoing access restrictions and monitoring similar to that required under the existing O&M plan and post-removal site control plan (RETEC 2007a) implemented for the T-117 Upland Study Area following the 2006 TCRA. Alternative 1, upland soil excavation and sediment excavation/dredging combined with capping This alternative involves the excavation of soil from the T-117 Upland Study Area, including the shoreline bank area, as well as the Adjacent Streets and Residential Yards Study Area. As set forth in Section 4, this alternative would include soil removal up to the MTCA-specified depth of compliance of 15 ft as needed to achieve the RvALs. The Upland Study Area would be backfilled to an elevation of +14 -ft MLLW, and the Adjacent Streets and Residential Yards would be backfilled to near original grades. In the T-117 Sediment Study Area, the portion of the mudflat sediment offshore of the toe of the shoreline bank and outward to an elevation of approximately 0 -ft MLLW would be excavated using conventional shore-based earth-moving equipment. The depth of excavation would be approximately 2 to 4 ft. Subtidal sediment removal in the Marina, would be approximately 2 to 5 ft deep, would beand be accomplishedremoved using over-water mechanical dredging to re-establish navigable depths within the Marina. Capping material would be placed throughout the sediment remediation area, except for the Marina, to establish a clean sediment surface in compliance with the sediment RvALs. Map 7-1 shows the Alternative 1 removal area excavation prisms. Alternative 2, upland soil excavation and sediment excavation/dredging This Alternative is the same as Alternative 1 regarding excavation and backfilling at the T-117 Upland Study Area and adjacent shoreline bank as well as the Adjacent Streets and Residential Yards Study Area. Alternative 2 only differs from Alternative 1 relative to the nature of the removal action in the Sediment Study Area offshore of the toe of the shoreline bank. Alternative 2 requires dredging of all contaminated sediment within the sediment boundary, including dredging within the Marina to re-establish navigable depths. Dredging depths will range from 2 to 7 ft. The dredged areas, except the Marina, will be backfilled with clean material to re-establish site grades. Map 7--2 shows the Alternative 2 removal area excavation prisms. Map 7-3 presents an overview of the removal areas and the sediment cap area of both Alternatives. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 198 Table 7-1. Summary of site-wide removal action alternatives Extent of Action and Action Goals Based on Preliminary RAOs Adjacent Streets and Residential T-117 Sediment Alternative Description T-117 Upland Removal Area Yards Removal Area Removal Area No Action Alternative. No Institutional controls (e.g., removal of contaminated access controls) material. Ongoing institutional Monitoring controls, monitoring and site- None None None wide maintenance would Site-wide maintenance continue as presently (inspections, erosion and required. surface water controls) RvALs based on a broad range of potential future upland site use Potential future upland site use Upland soil excavation conditions or use as upland habitat conditions and associated RvALs a are met based on MTCA and met. Combined excavation and Limited intertidal sediment background. dredging with capping to excavation in the mudflat Restore site to approximate premeet sediment RvALs at the toe of the Bank Alternative includes the baseline existing grades, with paving and Alternative 1. Upland soil within the T-117 sediment stormwater improvements meeting removal and sediment completion approach: backfill with Limited subtidal sediment removal area to the City of Seattle design codes. excavation/dredging clean soil to restore the site to dredging at the marina specified depth of intermediate elevation of just above Restore yards to pre-existing combined with capping compliance (45 cm). A Sediment capping to meet +14 MLLW to allow for broad range conditions and restore any thicker cap (e.g., up to 3 the sediment RAOs as of future uses (including possible improvements that exist at the time ft) could be required needed within the habitat development). Post removal of initiation of the cleanup. depending on final design. sediment boundary redevelopment options may be Restore yards to pre-existing chosen by the Port during the conditions. removal design (Section 9.3). Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 199 Extent of Action and Action Goals Based on Preliminary RAOs Adjacent Streets and Residential T-117 Sediment Alternative Description T-117 Upland Removal Area Yards Removal Area Removal Area Excavation and dredging to meet sediment RAOs within the T-117 sediment removal area to the Upland soil excavation specified depth of compliance (45 cm). Intertidal sSediment Capping would not be excavation between the used except as a Alternative 2. Upland soil bank and subtidal area contingency for limited removal and sediment Same as Alternative 1. Same as Alternative 1. areas where sediment excavation/dredging Subtidal sediment dredging to the extent of excavation or dredging the sediment boundary might not be feasible (e.g., around existing No capping structures). Backfilling with clean material would occur in some locations to restore the desired final topography. a According to MTCA unrestricted site use conditions, "Restrictions on the use of the site or natural resources affected by releases of hazardous substances from the site are not required to ensure continued protection of human health and the environment" (WAC 173-340-200).The point of compliance is typically throughout the site to a depth of 15 ft (WAC 173-340-740(6)). MTCA CULs are specific to each contaminant and are derived using default or site-specific assumptions as set forth for soil under WAC 173-340-740 (i.e., the Method A default CUL for total PCBs in soil for unrestricted land use is 1.0 mg/kg). Soil CULs for upland areas to be developed for use as habitat are set forth under WAC 173-340-7493 and may be more stringent than MTCA Method A. Reliance on clean soil covers to provide for habitat development may include requirements for institutional controls to maintain habitat areas and prevent exposure of sensitive species to residual site contaminants located at depth. Soil that is directly erodible into the LDW or that will come to reside within the aquatic portion of the LDW as a result of this removal action will meet sediment RvALs set forth herein. ARAR applicable or relevant and appropriate requirement MTCA Model Toxics Control Act RvAL removal action level CUL cleanup level na not applicable T-117 Terminal 117 LDW Lower Duwamish Waterway RAO removal action objective WAC Washington Administrative Code Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 200 Both alternatives include the extensive removal of contaminated soil and sediment to meet the RAOs. Both represent a high degree of cleanup, and neither depends on containment or institutional controls in the upland areas. In addition, there is the potential for encountering currently unknown site infrastructure, artifacts, and/or contamination during the removal action, which both alternatives will address, as appropriate. The use of controls or restrictions would only be used as necessary to protect future habitat in both the upland and aquatic areas. Alternative 1 would depend upon institutional controls (in the offshore cap area to help ensure the long-term integrity of these in-water structures. Alternatives 1 and 2 include the assumption that after upland and bank soil removal is completed to remove COCs at concentrations greater than the soil RvALs up to the appropriate depth of compliance (e.g., up to 15 ft below final upland site grade), the excavated portions of the T-117 Upland Study Area will be backfilled to a finished grade just above elevation +14 MLLW, which is slightly above the high water line of +13.8 ft MLLW. For the purpose of this EE/CA, this is referred to as the baseline completion option, which is necessary to develop cost estimates. Additional dDevelopment options for restoring the T-117 EAA that are compatible with a full range of possible future site uses (i.e., completion options), including habitat restoration, are discussed in Section 7.3. The following subsections describe the two removal action alternatives in detail and discuss how each would be implemented. Each alternative is discussed relative to specific actions within the three T-117 EAA three study areas and in terms of the overall criteria of implementability, effectiveness, and cost as defined in EPA's Guidance on Conducting Non-Time-Critical Removal Actions Under CERCLA (1993). The evaluation of each alternative includes a discussion of: Site preparation requirements Soil excavation activities Sediment excavation/dredging and capping activities Management of excavated and dredged materials Site completion and coordination with future site uses Quantities and costs Evaluation of implementability and effectiveness 7.1 ALTERNATIVE 1: UPLAND SOIL EXCAVATION AND SEDIMENT EXCAVATION/ DREDGING COMBINED WITH CAPPING This alternative involves the excavation of soil in the T-117 Upland Study Area (including the shoreline bank) and Adjacent Streets and Residential Yards Study Area Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 201 to meet the defined soil RvALs at the depths of compliance presented as the RAOs in Section 4.4. In the T-117 Sediment Study Area, mudflat sediment would be excavated using conventional land-based earth-moving equipment, and subtidal sediment would be removed using a barge-mounted dredge to allow for a sufficient postremoval cap depth. The subtidal (submerged) portion of the removal area would then be capped (except in the area offshore of the Marina, where removal without capping would be used to meet the RAOs). The specific combination of excavation and dredging would be established during the remedial design. Surface water quality monitoring parameters and criteria for dredging work would be identified as part of the design phase of the NTCRA. Capping would be used instead of excavation or dredging to address contaminated sediment at locations where capping could be implemented without unacceptable shallowing or constriction of the river channel or Marina. As mentioned previously, specific locations where final cap elevations would need to be consistent with required channel depths would be identified and evaluated during the remedial design. For the purpose of this EE/CA, it is assumed that a cap thickness of 3 ft would be used (see Section 7.1.3). The actual cap thicknesses and layers would be finalized as part of the NTCRA design and could vary depending on the location of the capped area. The first (bottom) layer of the anticipated cap cross section would consist of a 6-in. to 1-ft-thick layer of granular soil, which would serve as a filter layer and be placed directly on the sediment. Above this layer would be a 1- ft-thick layer of cobbles to provide stability and resistance to erosion. The final (upper) portion would consist of a 1-ft-thick layer of habitat-enhancing sand and gravel that would be appropriately sized for stability during normal river flows. 7.1.1 Site preparation Excavated and dredged materials will need to be removed from the site for offsite disposal (Section 7.1.4). A number of site preparation activities would need to be completed prior to the implementation of the removal action. Design details and work plans for implementation would be further developed during the design phase. Site preparation activities are described below. 7.1.1.1 Public notification and traffic control measures A traffic routing plan would be developed during the design phase with input from the community. Prior to work initiation, public notifications and traffic control measures would be implemented in accordance with the approved routing plan and site-specific construction plans. Notifications would inform the potentially impacted neighborhood residents and businesses of the planned construction dates, duration of work, areas of work, site access restrictions, and possible alternative traffic routes for neighborhood residents and construction trucks. Hours of operations (i.e., working longer hours for shorter overall duration or working shorter hours for potentially longer overall duration) will also be determined with community input. In addition, the timing of road improvement activities (e.g., the pending South Park Bridge replacement project) would need to be considered. Traffic control measures, including Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 202 signage, warning lights, and the use of traffic control personnel, would be implemented in accordance with applicable construction codes and guidance. 7.1.1.2 Dust control plan Control of offsite dispersal of dust generated during construction would will be a high priority for the NTCRA design and implementation. A dust control plan wouldwill be developed as part of the NTCRA design and would specify methods and criteria for implementing specific dust control measures. Dust control methods and monitoring activities similar to those used during the 2006 TCRA (RETEC 2006) wouldwill be evaluated for applicability to the site and used as appropriate. Monitoring of previous remedial actions has been conducted at the T-117 EAA. Air monitoring was conducted as part of the 2006 TCRA (RETEC 2006). Air sampling and monitoring for the TCRA consisted of air quality monitoring, meteorological monitoring, and odor observations. Air monitoring action levels weres specified in the air quality and meteorological monitoring plan18 (Appendix D in RETEC 2006). Monitoring before (background) and during removal identified particulate and PCB concentrations well below the action levels (RETEC 2007b). During the 2005 independent removal action conducted by the City, yard soil was removed at 8601 and 8609 Dallas Avenue S. During the removal, wipe samples were collected from metal and painted wood surfaces at the residences. The wipe samples were analyzed for PCBs, which were not detected above the PQL of 2 g/100 cm2 (Onsite Environmental 2005). Finally, WSDOH conducted indoor dust sampling in conjunction with the 2004-2005 independent removal action at two homes on 17th Avenue S (8601 and 8609 17th Avenue S). Dust was collected with a high- volume, small- surface sampler in areas of high activity in the homes. PCBs were detected (primarily in rugs) at levels ranging from 0.756 to 1.57 mg/kg (dust loading ranged from 2.18 to 16.7 g/m2), indicating that some PCBs were transported into the home from exterior sources (assumed to be Dallas Avenue S road dust). However, WSDOH concluded that no apparent public health hazard existeds for residents exposed to PCBs found in house dust along Dallas Avenue S (WSDOH 2006). Although previous monitoring has not identified significant issues with regard to dust, dust control and monitoring will be conducted during the removal action. Particular attention would will be given paid to controlling dust during excavation, soil loading activities, and work during dry weather. Meteorological monitoring would also be used as a tool for evaluating dust control needs. As was done for the TCRA, dust management may include the wetting of excavation areas and stockpiles with water, covering of trucks loaded with soil, covering of stockpiles that are not 18 The action level for PM10 particulates (as measured with DataRAM meters and TE-1000 polyurethane foam cartridge samplers) was 105 g/m3 based on a 24-hour average, and the action level for PCB concentrations was 0.11 g/m3 at the property perimeter. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 203 being actively loaded or unloaded, and daily sweeping of onsite truck routes and soil handling areas. Meteorological monitoring would also be used to evaluate dust control needs. Odor was not an issue during the 2006 TCRA, but odor control foam will be applied during the NTCRA if odor problems arise. The monitoring methods will be developed in the NTCRA design phase. 7.1.1.3 Construction mobilization Supporting site facilities, staging areas, drainage and erosion controls, dust suppression equipment and effective decontamination facilities, including facilities for truck wheel washing, would be installed or constructed prior to the initiation of the removal action. Plans for site health and safety, drainage controls (Section 7.1.1.4), construction scheduling, dust and track-out monitoring and control, in-water monitoring (during dredging/capping) and other measures will need to be prepared and fully implemented. Measures will also need to be in place to ensure that truck loads are appropriately lined and covered and vehicles are decontaminated (i.e., wheels have been washed) and inspected prior to leaving the T-117 EAA and entering public streets. 7.1.1.4 Water control systems Collection, treatment, and disposal systems will be required to address surface runoff coming into or originating from the removal areas. Engineered well-point systems and/or subsurface barriers or interceptor systems would also likely be necessary to limit the influx of groundwater into deeper upland excavations within the T-117 Upland Study Area. A shoreline barrier (i.e., sheet pile wall or soil berm) would be employed as needed to limit tidal influence of groundwater and prevent tidal inundation of upland soil removal areas. For the purpose of the EE/CA, it is assumed that either an upgradient low-permeability cutoff wall (i.e., bentonite/ cement slurry-filled trench) or a groundwater dewatering system would be used to limit groundwater influx from upgradient areas prior to excavation below the water table. Additional water extraction and treatment would likely be necessary for any water that may collect within temporary shoreline/bank barriers (e.g., a sheetpile walls) and the deeper inland soil removal prisms in order to maintain desired work conditions, prevent water intrusion, and facilitate backfilling. A construction site stormwater management plan would be prepared for the project and would include soil staging areas, the location and design of water storage/treatment facilities, and any associated sediment handling facilities. The plan would specify methods for intercepting, collecting, and managing stormwater, as necessary. BMPs, including the covering of excavated materials, stormwater interception, and collection and treatment of water from excavation and staging areas, will be used to ensure that potential impacts to the adjacent river, properties, and existing residential drainage systems are controlled. The City and County permitting requirements for offsite disposal of collected and treated water will be considered in developing and implementing water management systems. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 204 7.1.1.5 Staging areas Staging areas for excavated soil would be established within the T-117 EAA, as necessary, to accommodate material storage and loading. Staging will have to be carefully managed for the T-117 Upland Study Area excavation because available space will be limited; the project design will need to consider off-site staging and the direct loading of trucks. Bank soil and sediment excavated using land-based equipment would also be staged and loaded for transport within the confines of the T--117 Upland Study Area. Sediment removed using over- water dredging would be transported to an appropriate shoreline transfer location at an existing dock along the LDW or at a Port facility, depending on availability of suitable space. Another option would be to transfer dredged sediment using a specially constructed temporary transfer facility at the T-117 EAA. Safeguards to ensure the clean and safe transfer of materials would be required for the sediment handling location. Temporary material staging time frames for soil or sediment deemed to be hazardous waste would be consistent with limits set forth under RCRA for remediation wastes (typically 90 days unless additional time is authorized by EPA), and the staging location would comply with staging pile rules (WAC 173-303-64690 and 40 CFR 264.554). Bank soil and sediment will be excavated first and will be stored on the T-117 Upland Study Area, in a soil-staging facility, which will be lined and bermed. As mentioned above, the construction site stormwater management plan would include control measures for soil/sediment staging areas and any associated sediment transfer facility. 7.1.1.6 Demolition and removal or relocation of structures and utilities The T-117 Upland Study Area and Adjacent Streets are paved and include buried slabs, utility corridors, storm drains, and other subsurface features. The north, central, and south buildings at the T-117 EAA and associated shelters, loading docks, and foundations would be demolished and removed during the initial stage of the NTCRA. Closed-in-place USTs located within the projected excavations, the UST in the vicinity of the southwest corner of the north building, and the septic tank that serves the north building and most of the associated drain field to the south would be removed as part of the NTCRA. The decision to remove any additional portions of the septic drain that may be encountered beyond the planned limits of the T-117 Upland Removal Area would be based on field observations and performance sampling results at the time of the NTCRA. The Adjacent Streets would be closed in stages to allow access to the T-117 Upland Study Area and to limit the disruption of residential access. A portion of the Marina floating docks would be temporarily relocated out of the T-117 sediment removal area to an alternate location based on timing and availability of moorage space. This relocation will allow for access to sediment within the northern end of the sediment removal boundary. The Adjacent Streets would be temporarily vacated, as necessary, to allow for the removal of underlying soil. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 205 7.1.1.7 Yard remediation The Residential Yards are not owned by the City or the Port; therefore, access agreements would need to be established prior to the initiation of any remediation on these private properties. Also, the Residential Yards are landscaped and include fences, utilities, and other surface and subsurface features. These features would need to be removed or worked around if they are located within the excavation prism. Removal activities would be coordinated with property owners prior to initiation and would be conducted in such a manner as to limit the disruption of residential access. Specific procedures for coordination with affected property owners would be developed with community input during the remedial design phase. Any landscaping that is disturbed will be replaced and/or replanted, and surface drainage will be maintained or improved as necessary. 7.1.2 Soil removal The estimated boundary of the removal action in the T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area is presented on Map 4-1. The estimated extent of the removal action in the T-117 Upland Area and Adjacent Streets is are presented in Maps 7-1 and 7-3. The spatial extent of the removal action is designed to address COCs in the upland soil (see Section 4) and include the removal of the berm of the shoreline bank. Figures 7-1 through 7-5 show the extent of the proposed NTCRA in a series of cross sections. The T-117 Upland removal area is composed of several excavation prisms with depths that range from 1 to 17 ft. The Adjacent Streets and Residential Yards removal area is composed of several excavation prisms that range in depth from 1 to 6 ft along portions of the Adjacent Streets and up to 2 ft within specific Residential Yards. The locations and depths of excavations may be expanded slightly during design to provide for equipment access, slope stability, and sequencing of the excavation process. The modification of excavation locations and depths may also be necessary to address unforeseen conditions encountered during removal, including the presence of structures (e.g., underground utilities). As described in Section 9.3.3.2, final depths will be based on confirmation sampling to ensure that the RvALs are attained. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 206 Slipsheet for 11 x 17 Figure 7-1. Cross section E1 for Alternative 2 Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 207 Slipsheet for 11 x 17 Figure 7-2. Cross section E2 for Alternative 2 Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 209 Slipsheet for 11 x 17 Figure 7-3. Cross section E3 for Alternative 2 Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 211 Slipsheet for 11 x 17 Figure 7-4. Cross section E4 for Alternative 2 Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 213 Slipsheet for 11 x 17 Figure 7-5. Cross section E5 for Alternative 2 Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 215 The yard and street DUs designated for removal are identified based on UCL calculations from MIS sampling results (as detailed in Appendix L, and described in Section 4.4.3).19 The Adjacent Streets and Residential Yards Study Area is composed of several excavation prisms that range in depth from 1 to 6 ft along portions of the Adjacent Streets and up to 2 ft within specific Residential Yards. Pre--removal sampling is anticipated in Residential Yards as part of the design phase to pre- determine the extent of soil removal from yards and at DU25 and DU35, where soils adjacent to a DU designated for removal have not been characterized. The DUs designated for removal and the locations for pre-removal sampling are shown on Map 7-3. The approximate in-place (i.e., pre-excavated) volumes of soil anticipated to be removed from the T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area are presented in Table 7-2. Table 7-2. In-place volumes of soil and sediment to be removed and estimated sediment capping/backfilling volumes under Alternative 1 a b Study Area Component Quantity (cy) non-TSCA soil 33,100 T-117 Upland Study Area TSCA-designated soil 3,900 non-TSCA soil 7,400 Adjacent Streets TSCA-designated soil 900 non-TSCA soil 1,800 Residential Yards TSCA-designated soil 0 non-TSCA soil 42,300 Total soil to be removed TSCA-designated soil 4,800 non-TSCA sediment 6,450 Total T-117 Sediment Study Area TSCA-designated sediment 50 Material required for capping/backfilling 8,000 a TSCA soil is defined as soil with total PCB concentrations 50 mg/kg. A portion of this volume, approximately 250 cy, is estimated to contain total PCBs at concentrations 500 mg/kg. According to TSCA, all soil 50 mg/kg is amenable for disposal in accordance with 40 CFR 761.61(a)(5)(iii): "Bulk PCB remediation wastes with a PCB concentration 50 ppm shall be disposed of in a hazardous waste landfill permitted by EPA under section 3004 of RCRA, or by a State authorized under section 3006 of RCRA, or a PCB disposal facility approved under this part." Final offsite disposal is subject to review by EPA and will be arranged in accordance with the waste-acceptance policy of the approved disposal facility. b Total volumes include the complete removal of the asphalt and base course material, as necessary, within the T-117 Upland Study Area and Adjacent Streets. cy cubic yard EPA US Environmental Protection Agency PCB polychlorinated biphenyl TSCA Toxic Substances Control Act 19 An option exists to collect additional replicate samples at DUs with only one MIS sample. Based on additional sampling results and the recalculation of the UCL, the status of the corresponding DUs could change. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 217 Total volumes include the complete removal of the asphalt and base course material, as necessary, within the T-117 Upland Study Area and Adjacent Streets. As shown in Table 7-2, some of the soil from the T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area will be TSCA-regulated waste, requiring disposal at a Subtitle C landfill. The majority of the volume will be suitable for disposal at a Subtitle D landfill. Excavation stability, impacts to groundwater, stormwater controls, and tidal water intrusion will be addressed in the design phase of the NTCRA. The design phase will also address proper sequencing and the selection of effective construction methods (i.e., use of temporary shoreline soil berms, sheet piling, or other types of barriers) and surface water and groundwater controls. The locations and depths of the soil removal prisms will be refined during final design and execution based on site conditions. The majority of the soil within the T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area consists of loose-to-medium-dense silty gravelly sand, with deposits of sand and silt. Based on this soil type, excavation slopes of 2 horizontal to 1 vertical (2H:1V) were assumed and included in the estimated upland soil volumes. The refinement of excavation slopes and methods will be included in the design phase of the NTCRA. Confirmation sampling in the T-117 Upland Study Area will be conducted at the limits of excavated areas and compared to RvALs removal action levels for target COCs. Confirmation sampling of the Adjacent Streets and Residential Yard Study Area soils will include PCBs and dioxins/furans (see Section 9.3.3.2). The removal of the shoreline berm material will be carried out as part of the removal action in the T-117 Upland Study Area. The portion of the bank to be removed is included within the T-117 Upland Study Area boundary (Map 4-1). All soil that may remain beneath the re-established (i.e., new) bank portions of T-117 EAA completed above +13.8 ft MLLW will meet the applicable soil RvALs to the compliance depth (i.e., up to 15 ft below final ground surface) set forth in Section 4 and shown on Figure 4-1. Most of the upper portion of the bank will be removed and replaced with clean fill that will meet the sediment RvALs. In addition, these actions will ensure that all bank soil that could become intertidal or subtidal sediment (i.e., upon completion of the NTCRA) will meet the applicable sediment RvALs to the specified depth of compliance, either through dredging or a combination of dredging and capping depending upon the selected removal alternative. It is anticipated that some additional bank removal (i.e., soils with COCs concentrations less than the RvALs) may need to be undertaken at some locations to ensure the stability of completed (i.e., new) shoreline banks and accommodate possible final site uses (e.g., aquatic habitat). 7.1.3 Sediment removal and capping Alternative 1 includes the removal of sediment from the mudflat close to the bank and above elevation 0 ft MLLW following the removal of the impacted bank material (based on appropriate soil or sediment RvALs) and the dredging of impacted Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 218 sediment from within the Marina (and also re-establishing navigable depths in Marina). This would be followed by the capping of the mudflat and submerged areas within the sediment removal boundary except within the Marina, which would be an impediment to navigation. Removal will be accomplished by excavating a portion of the contaminated sediment and debris from the mudflat (e.g., down to elevation 0 ft MLLW). Capping designs prepared in accordance with USACE guidance (see Section 6.1.2.2) for PCB- contaminated sediment can include caps that range from 12 to 36 in. thick. The caps are often multi-layered to provide chemical isolation immediately over the impacted sediment and include a sand and gravel/cobbles layer to prevent erosion from waves and prop wash and a surficial habitat layer of sand and gravel. A robust 3-ft- thick cap configuration has been assumed for the EE/CA. The cap would consist of three layers: a sandy material to provide primary physical and chemical containment of the underlying sediment, an armored layer (cobbles) to protect against erosion, and a surface layer of natural sand and gravel. The final cap design will be based on a hydraulic evaluation to determine an acceptable river channel cross section. The cap construction could also include the placement of a filter layer (fabric in the intertidal zone and granular soil in the subtidal zone). A conceptual cap design for T-117 is shown on The portion of Alternative 1 that would be capped is shown on Map 7-23 (plan view) and Figure 7--6 (cross section). The sediment exposed by the mudflat excavation would be sampled and analyzed for COCs and then capped as shown on Figure 7-6 unless post-removal testing showed that COC concentrations in the exposed sediment were less than the RvALs, in which case it would be backfilled using clean material. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 219 Slipsheet (11x17) Figure 7-6. General sediment excavation and cap cross section Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 221 Removal of sediment from within the T-117 Sediment Removal Area will likely be performed after the T-117 Upland Study Area work, which will help ensure that work in the T-117 Upland Study Area does not act as a source of recontamination to the sediment. For the purpose of meeting the RAOs for sediment (Section 4), once the mudflat excavation is complete, the new mudflat surface and submerged portion of the removal area will be capped. The volume of sediment to be removed under Alternative 1 is summarized in Table 7-2. Sediment removal and capping in the intertidal mudflat area would be completed using land-based excavators or dredges. Removal in the submerged portion of the T-117 sediment removal area would be completed using dredges and barges, working at higher tides as needed to provide the required draft for the barges. For the portion of the T-117 sediment removal area that is within the Marina, the submerged-zone impacted sediment will be removed and not capped or backfilled to re-establish navigation depths. Engineering controls will be implemented to limit the resuspension of contaminated sediment during removal. A primary method for minimizing sediment resuspension during removal in the intertidal zone is to complete the work when the tides are out while the sediment is exposed to the air. Using this approach, removal does not occur in the water column, and resuspension is essentially eliminated. The excavation process will occur over a few weeks' time, and portions of the excavation will be inundated by the daily rising tides prior to the completion of the removal. Experience with this method of excavation over multiple tidal cycles at the Hylebos Waterway, part of the Commencement Bay Nearshore/Tideflats Superfund site, at several locations (General Metals Graving Slip, J&G Marina, Dunlap log ramp, Arkema South East Shoreline), demonstrated that the repeated inundation of the excavation area did not adversely impact the cleanup (DOF 2009). Engineering controls to limit suspension during dredging include the use of enclosed dredging buckets to limit wash out during retrieval of the bucket through the water column, and the avoidance of overflow of turbid sediment from the sediment haul barge during dredging. Other examples of engineering controls include using slower cycling times and containment structures to catch bucket spillage and direct materials into the receiving barge or platform. These techniques have been used at other sediment remediation projects in the LDW and other waterways. The use of silt curtains at the T-117 Sediment Study Area is not considered practical because of the varying river currents and tidal stages. Deploying, maintaining, and working with a silt curtain within the intertidal portion of the T-117 Sediment Study Area would be problematic, and the use of a silt curtain in the subtidal portion of the study area could interfere with navigation in the channel. According to an evaluation of resuspension controls for dredging (Bridges et al. 2008), the installation and maintenance of silt curtains in "moderate- or high-energy areas" can be difficult, and their effectiveness is questionable. Silt curtains that are not fastened to the bottom of Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 223 the river, which would be extremely difficult to do at the T-117 Sediment Study Area, can allow particles to escape beneath the skirt. Water quality will be periodically regularly monitored during dredging activities to assess potential water quality impacts during project implementation. Water quality conditions must be within the limits prescribed by EPA's 401 Water Quality Certification. If necessary, appropriate adjustments to dredging activities, such as those described above, will be made to maximize the protection of the environment. The mudflat excavation will start at the toe of the bank at an elevation of approximately +5 ft MLLW. The mudflat will be removed to an elevation of 0 ft MLLW and then extended horizontally to the existing 0 ft MLLW contour. By setting the deepest extent of the mudflat excavation at 0 ft MLLW, all of the nearshore excavation could be completed "in the dry" while the tides are out (< 0 ft MLLW). Typical sediment cap designs include layers of granular material designed to contain the contaminated sediment, protect against disturbance, and provide surficial habitat. The cap construction could include the placement of filter layer (fabric in the intertidal zone and granular soil in the subtidal zone) followed by the placement of quarry spalls and a surface layer of sand and gravel. The final cap configuration will include a hydraulic evaluation to determine an acceptable river channel cross section during the design phase of the NTCRA. A conceptual cap design for T-117 is shown on Map 7-2 (plan view) and Figure 7-6 (cross section). The duration of the marine construction for Alternative 1, for in-water dredging and capping, is estimated to be 20 to 25 working days. Institutional controls would be required for thea cap under Alternative 1 (to reduce the potential for the disturbance of the cap. Furthermore these controls would and require monitoring and maintenance. The cap would be designed to withstand smallvessel anchorage, fishing, or clamming activities. In addition, the institutional controls would be developed so as to not to affect tribal treaty fishing rights. Individual institutional controls may have limited effectiveness, and thus multiple controls are typically used to ensure long-term effectiveness. If Alternative 1 is implemented, then the details of the institutional control elements would be developed in an institutional controls implementation plan during design, and the controls would be anticipated to include proprietary controls (i.e., restrictive covenants), enforcement tools (i.e., agency orders requiring monitoring and maintenance), and informational devices (i.e., deed notice and state registry) as described below: Restrictive covenants would include restrictions on the capped area(s), limited by what is allowed due to the unique status of portions of the LDW as property formerly under the jurisdiction of the KCCWD1. To the extent possible, covenants would limit disturbance of the cap under Alternative 1. Actions such as construction projects that could disturb the cap would require agency approvals, management plans for controls, and restoration of the cap or complete removal of the contaminated materials. Restrictive covenants or other Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 224 agreements would also require agency notification of any pending sale of the property or any use of the property that might affect the cap, and provide for agency access. The restrictive covenants could "run with the land" and be included in any lease, deed, license, easement, or other use authorization. Specifically, City easements associated with the re-location of the power pole and future stormwater discharge drainage/outfall areas would be subject to the restrictive covenants placed on the upland property. Agency orders (an enforcement tool) would be an institutional control that is anticipated to be implemented under Alternatives 1 and 2. The Port and City would sign a CERCLA order with EPA that would require long-term monitoring and maintenance of any capped areas, as applicable. The details of the monitoring and maintenance requirements would be developed during design in an Agency-approved OMMP. EPA would review the effectiveness of the remedy, including monitoring results and institutional control implementation, no less frequently than once every 5 years, as required under CERCLA. Informational devices would be an additional institutional control for any capped areas under Alternatives 1 or 2. Deed notices describing the restrictions on the property would be filed in the King County Recorder's Office. Placement and maintenance of site information on the state registry (Ecology's Hazardous Sites List Site Register) would also provide informational tools regarding restrictions on the property. 7.1.4 Management of excavated and dredged materials Soil and sediment designated as a TSCA waste (i.e., with total PCB concentrations 50 mg/kg) will be the first material to be removed from each study area and disposed of at a Subtitle C landfill. Soil and sediment determined to be nonhazardous /non-dangerous will be disposed of at a Subtitle D landfill. These landfills have the ability to receive soil or wet dredged sediment delivered by rail. Both types of facilities must have also received the required EPA approval for acceptance of sediment and soil generated at CERCLA sites. EPA's approval takes into account the facilities' compliance with TSCA and/or RCRA permits and governing regulations, including the Off-Site Rule (40 CFR 200.440). The hauling of material from the T-117 EAA to the disposal site will result in increased truck traffic on neighborhood streets for the duration of the removal phase. A traffic routing plan will be developed during the NTCRA design phase with community input, as discussed in Section 7.1.1.1. The approved routing plan, as well as transportation and safety plans, will be developed by the contractor as part of the removal action work plan documents. These plans will address hours of operations; estimated numbers of trucks and barges required for soil and sediment hauling; Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 225 anticipated transport routes; material spill prevention, containment, and response plans; and other protective and mitigating elements. 7.1.5 Completion of the removal action and coordination with future site uses A principal goal of the removal action is to complete the T-117 Upland Study Area and T-117 Sediment Study Area in a manner that leaves them suitable for a range of final site uses and redevelopment options. An evaluation of final site redevelopment options is currently being performed by the Port and may be ready for implementation concurrent with the completion of the NTCRA or at a date after the NTCRA has been completed. Regardless, the NTCRA design measures will ensure that following the completion of the removal action, the ongoing integrity of the property will be maintained through slope stabilization, stormwater infrastructure, and erosion control measures. Under Alternative 1, it is assumed that the T-117 Upland Study AreaEAA will be restored to a baseline condition that has been backfilled and graded to a minimum elevation of +14 ft MLLW. This completion condition (hereafter referred to as the "baseline completion option") is assumed in this EE/CA was used here for costing purposes, inasmuch as it represents a "mid-point" from which a range of final site uses could be accommodated. These final site uses include future commercial uses that could be accomplished through limited additional backfilling, or the creation of intertidal habitat that could be accomplished through minimal backfill removal and contouring. These completion options are discussed further in Section 7.3. If the Port is able to identify a site redevelopment option in conjunction with community involvement prior to or during the design phase of the NTCRA, the design of the NTCRA completion would be coordinated with the final site use design. Restoration of this area will trigger the County's requirements and standards for surface and stormwater management (King County Ordinance 16264, 2009). The Adjacent Streets and Residential Yards Study Area will be restored to original grades and repaved and/or re-landscaped following the removal action. In addition, the restoration of this area will trigger the stormwater requirements of SMC 22.800 and Development Director's Rules 2009-005 (SPU), 17-2009 (DPD) (City of Seattle 2009a). It is anticipated that stormwater will use one or a combination of possible stormwater drainage, treatment, and potential discharge measures, including swales, underground vault treatment, or catch basin inserts. The final configuration of the stormwater collection and treatment system will be determined based on implementability, effectiveness, and cost and evaluated to minimize negative impacts on the final site use. Because the final configuration of the roadway stormwater improvements is an equal component of both Alternatives 1 and 2, it does not affect the comparison of alternatives for the NTCRA. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 226 7.1.6 Summary of estimated costs The total estimated cost for Alternative 1 is approximately $31.70.4 million (Table 7-3), which includes the present-worth cost for an assumed number of four cap-monitoring events over 10 years. The actual frequency of monitoring will be determined later as part of the post-NTCRA monitoring plan (Section 9.54) and may vary slightly from this assumption. A detailed breakdown of the estimated direct capital costs, indirect costs, long-term O&M costs and assumed contingencies is provided in Appendix J. Table 7-3. Summary of estimated costs for Alternative 1 a Study Area Estimated Cost T-117 Upland Study Area $20,100,000 Adjacent Streets and Residential Yards Study Area $76,6300,000 T-117 Sediment Study Area $4,000,000 Total estimated cost $310,7400,000 a Assumes baseline completion option for T-117 Upland Study Area with site restored to meet MTCA unrestricted cleanup and habitat protection criteria. MTCA Model Toxics Control Act O&M operation and maintenance T-117 Terminal 117 7.1.7 Evaluation of Alternative 1 This section discusses the implementability and effectiveness of Alternative 1 and provides a basis for the comparison of removal action alternatives presented in Section 8. The assessment of implementability includes consideration of: Technical feasibility and availability of technologies Administrative feasibility Public acceptance Cost Criteria for assessing effectiveness considered here and in Section 8 include both shortterm and long-term effectiveness. Long-term effectiveness includes consideration of: Overall protection of human health and the environment Ability to achieve RAOs Compliance with ARARs (including tribal treaty-protected resources) Reduction of contaminant toxicity, mobility, and volume 7.1.7.1 Implementability The successful implementation of Alternative 1 will depend on effective planning and the proper phasing of the work. The safe control of traffic and removal activities within adjacent residential streets and the control of dust generation and offsite Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 227 dispersion are examples of important factors to be considered. Soil excavation and sediment removal will be implemented using established and proven technologies that are readily available. The depth of soil removal in the upland portion will be accomplished using appropriate dewatering, shoring, staging, and material handling techniques. The alternative does not include any technologies that are experimental or unproven. Nevertheless, the depth of soil excavation, presence of shallow groundwater, and proximity of removal activities to the LDW can present challenges for upland excavation that will have to be addressed through careful planning and execution, including the potential use of physical barriers to control groundwater, a well-point dewatering system, and an associated water treatment system. Sediment removal will also need to be conducted in a highly controlled manner and with regard for specific scheduling constraints (e.g., fish windows). An assessment of the administrative implementability of Alternative 1 must include consideration of the multiple jurisdictions and regulations applicable to one or more of the study area settings or particular features in which the action will be implemented (i.e., the T-117 Upland Study Area, the Adjacent Streets and Residential Yards Study Area, and the T-117 Sediment Study Area). Some of the site, for example, is located within the County, and the remainder is within the City. The T-117 Sediment Study Area is located within the sediment portion of the LDW; other areas are made up of city street ROWs. As presented in Appendix G, there are a number of ARARs and substantive requirements that include measures to safeguard aquatic resources that must be considered prior to and during the removal action. Construction and permanent maintenance easements will also be required for the installation of a power pole and associated power lines, and stormwater features on the T-117 Upland Study Area (see Section 7.3). Access agreements must also be established with those property owners whose yards require remediation. 7.1.7.2 Effectiveness Alternative 1 will be highly effective in terms of protecting human health and the environment, complying with ARARs and achieving RAOs, including meeting criteria for a broad range of possible future land uses and protection of terrestrial habitat, where applicable. Contaminants that might otherwise migrate to the adjacent LDW will be removed through the excavation of contaminated soil from the upland portions of the T-117 EAA. Alternative 1 will remove source materialcontaminated soils, including thatparticularly those in direct contact with groundwater and or that could possibly come into contact with stormwater, as well as contaminated those present in sediment. It will also include measures to address potential site recontamination. Short-term risks posed byin the proposed removal action exist because of the large size and depth of the excavations. Engineering controls to prevent secondary impacts of soil excavation and transport and sediment dredging and capping will be included as part of the alternative. Special measures, including shoring, and dewatering will likely be required to control groundwater influx that would otherwise occur in deep excavations (i.e., those extending into the saturated groundwater zone). The removal Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 228 of contaminated bank materials and upland soil in the vicinity of the bank will require special safeguards to limit the potential for impacts on the adjacent LDW. These will include working during low tides and the use of berms, temporary covers (sand/fabrics), or sheet pile walls to isolate work areas. Other short-term risks include the potential exposure of onsite workers and nearby neighbors to contaminants through the ingestion of or dermal contact with soil or through the inhalation of airborne dust. Proven safeguards are available to mitigate these risks and include the use of protective clothing for workers and measures such as dust control and monitoring and track-out prevention to protect the surrounding community. These and other safeguards that will be set forth in a site-specific health and safety plan developed concurrently with the NTCRA work plan. Of particular importance is the risk to public health and the environment that could result from air emissions (i.e., dust) during limited time periods. Dust could migrate from T-117 to the surrounding community during grading activities. To mitigate potential dust risks, engineering controls such as water sprays will be employed, as necessary, during construction to ensure that dust and particulates are within acceptable regulatory levels. Perimeter air monitoring will be performed during the removal action to monitor potential exposure to the public during excavation. Control of odors that may be generated from the removal of the impacted soil will also be addressed through the use of engineering controls similar to those used for dust. These control measures, together with specific criteria for their application, will be included in the NTCRA health and safety plans. The long-term effectiveness and permanence of Alternative 1 is expected to be moderately high. Under this alternative, RAOs will be met even if sediment concentrations at depth remain above SMS criteria because potential exposure will be limited by clean backfill or capping. However, these materials could potentially become exposed if overlying cover materials were inadvertently disturbed. Institutional controls would be required under Alternative 1 to reduce the potential for the disturbance of the cap and require monitoring and maintenance. Caps would likely include an armor layer that would be covered with a sediment layer designed to withstand small- vessel anchorage, fishing, or clamming activities, with an institutional control requiring cap monitoring and maintenance. Institutional controls would be developed so as to not affect tribal treaty fishing rights. The details of institutional controls would be set forth in an institutional controls implementation plan, as described in Section 7.1.3. INSTITUTIONAL SAFEGUARDS TO PROTECT THE IN-WATER CAPS (I.E., RESTRICTIVE COVENANTS AND MONITORING) WOULD BE NEEDED TO PROTECT AGAINST THE POSSIBILITY OF CAP DISTURBANCE FROM ACTIVITIES SUCH AS BOAT ANCHORING. THE CAP WILL INCLUDE AN ARMOR LAYER THAT WILL PROTECT IT FROM DISTURBANCE BY TYPICAL BEACH USE, FISHING, AND CLAMMING THE SELECTION OF SAFEGUARDS AIMED AT LIMITING CAP DISTURBANCE WOULD BE Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 229 DETERMINED BASED ON THE SPECIFIC ACTIVITIES THAT THEY SEEK TO CONTROL, AND THE EFFECTIVENESS OF THESE SAFEGUARDS WOULD DEPEND ON THE EXTENT TO WHICH THEY ARE ENFORCED. 7.2 ALTERNATIVE 2: UPLAND SOIL REMOVAL AND SEDIMENT EXCAVATION AND DREDGING As mentioned previously, Alternative 2 is the same as Alternative 1, except that capping would not be used as an alternative sediment containment measure within the T-117 Sediment Study Area for the purpose of meeting the prescribed sediment RAOs. Instead, the RAOs would be met solely through a combination of sediment excavation and dredging followed by backfilling with clean materials. Clean fill materials will be used to restore the aquatic portions of the site to original grades (except in the Marina), to backfill the T-117 Upland Study Area to an elevation of approximately +14-ft MLLW, and to re-establish site grades in the Adjacent Streets and Residential Yards Study Area. 7.2.1 Site preparation The same preparation activities described for Alternative 1 would be required for Alternative 2. Areas for sediment handling and transfer equipment capacities might need to be slightly larger to accommodate the increased material volumes from dredging areas that would otherwise be capped in Alternative 1. 7.2.2 T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area removal activities The Alternative 2 removal activities for the T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area are the same as those described for Alternative 1. The approximate in-place volumes of soil anticipated to be excavated from the T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area are listed in Table 7-2. The estimated extent of the removal action in the T-117 Upland Study Area and Adjacent Streets is presented on Maps 7-2 and 7-3. 7.2.3 T-117 Sediment Study Area removal activities Alternative 2 is the same as Alternative 1 regarding excavation and backfilling at the T-117 Upland Study Area and adjacent shoreline bank as well as the Adjacent Streets and Residential Yards. Alternative 2 only differs in the sediment removal area offshore of the toe of the shoreline bank as shown on Maps 7-2 and 7-3. Alternative 2 requires the dredging of contaminated sediment within the sediment boundary, including dredging within the Marina to re-establish navigable depths within the Marina. The dredged areas, except the Marina, will be backfilled with clean material to re-establish site grades. A limited amount of sediment within the rock riprap along the toe of the Marina shoreline contains elevated PCBs (i.e., samples Trans- A-sed, Trans- B-sed, and 99-G, as shown on Map 2-8). Rather than removing the riprap and undermining the Marina shoreline, the sediment within the rip rap may be removed (manually at low tide or by divers) or contained by a localized cover. The excavation and dredging Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 230 contours for Alternative 2 are presented on Map 7-12 and shown on cross sections presented as Figures 7-1 through 7-4. Dredging volumes under Alternative 2 will be greater than those for Alternative 1 because all of the subtidal area is dredged under Alternative 2. The dredged areas will be backfilled to re-establish aquatic site grades so there is no net impact to aquatic habitat elevations. The surface layer of backfill material will be imported, clean, uncrushed sand and gravel of the appropriate size and composition to remain stable under the range of LDW currents and maritime activities (e.g., boat wake, prop wash). It is anticipated that the backfill would be placed with floating equipment, working at higher tides, as necessary, to provide the needed draft for barges. The volume of sediment to be removed and backfilled under Alternative 2 is summarized in Table 7-4. Table 7-4. In-place volumes of sediment to be removed and estimated sediment backfill volumes under Alternative 2 a Study Area Component Quantity (cy) non-TSCA sediment 13,950 T-117 Sediment Study Area TSCA sediment 50 Total sediment to be removed 14,000 b Material required for backfilling 10,000 a TSCA sediment is defined as sediment with total PCB concentrations 50 mg/kg. b No backfilling in the Marina (approximately 4, 000 cy). cy cubic yard PCB polychlorinated biphenyl TSCA Toxic Substances Control Act The duration of the marine construction for Alternative 2, for in-water dredging and backfilling, is estimated to be 30 to 35 working days. Dredging safeguards, material transfer, and monitoring would be the same as those presented for Alternative 1. 7.2.4 Landfill disposal of excavated and dredged materials Methods used for the management and disposal of excavated and dredged materials under Alternative 2 are the same as those described for Alternative 1. The larger volume of sediment removed under Alternative 2 will need to be considered in specifying the operating parameters and sizes for the sediment handling and transfer areas. 7.2.5 Site completion and coordination with future site uses As with Alternative 1, under Alternative 2, the T-117 Upland Study Area will be backfilled to an elevation of at least +14 ft MLLW. However, final site design may change slightly depending on the timing of the ongoing evaluation and the selection of the final site use (see Section 9.2). Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 231 7.2.6 Summary of estimated costs The total estimated cost for Alternative 2 is approximately $331.29 million (Table 7-65). A detailed breakdown of the estimated costs and assumed contingencies is provided in Appendix J. Table 7-65. Summary of estimated costs for Alternative 2 a Study Area Estimated Costs T-117 Upland Study Area $20,100,000 Adjacent Streets and Residential Yards Study Area $76,6300,000 T-117 Sediment Study Area $5,500,000 Total estimated cost $331,2900,000 a Assumes baseline completion option for the T-117 Upland Study Area with the site restored to meet MTCA unrestricted criteria. EAA early action area O&M operation and maintenance T-117 Terminal 117 7.2.7 Evaluation of Alternative 2 This section discusses the implementability and effectiveness of Alternative 2 and provides a basis for the comparison of removal action alternatives presented in Section 8. 7.2.7.1 Implementability The implementability of Alternative 2 is very similar to that of Alternative 1. The additional dredging of sediment associated with Alternative 2 will require some additional in-water construction time (10 to 15 working days), which could extend the duration of the removal action to accommodate seasonal restrictions on in-water work. 7.2.7.2 Effectiveness The long-term effectiveness of this alternative is expected to be high. Sediment that contains COCs above the action level will be removed, resulting in a higher degree of effectiveness and permanence than that for Alternative 1 (Section 7.1.7). 7.3 PROJECT COMPLETION OPTIONS EPA has mandated site-specific goals for the removal action in the T-117 Upland Study Area. One of these goals is to develop removal alternatives that are consistent with a wide range of final site uses, not just those limited to industrial activities. The Port is examining commercial development and habitat restoration alternatives for Port property within the LDW, which includes the T-117 EAA, in coordination with the appropriate agencies. This section describes two alternative site completion options (Options A and B) that could be implemented following the NTCRA. These completion options could Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 232 accommodate a variety of future uses and would replace the baseline completion option that was included in the two removal action alternatives for costing purposes. The baseline completion option was assumed for the removal alternatives because it represented a mid-point among the range of possible final site use configurations. The two completion options presented here provide for a broad range of configurations and topography to accommodate a wide variety of potential post-NTCRA developments. It is expected that a final site use will be identified in time to be incorporated into the NTCRA during the design phase. If this occurs, the baseline completion option would not be implemented, and the final NTCRA design would include restoration of the site to final grades appropriate to accommodate the selected final site use. Soil excavation and sediment dredging or dredging/capping would still be conducted to meet the RvALs within the removal areas and to the necessary compliance depths relative to the completed (final) topography. The baseline completion option described below and two alternative completion options would all be protective and would meet the RAOs established for the T-117 removal action set forth in this EE/CA. Option A, Restore the T-117 Upland Study Area to existing elevation Under this option, removal excavations in the T-117 Upland Study Area would be backfilled to achieve surface elevations similar to those of the existing T-117 Upland Study Area (elevation of approximately +18 to +21 ft MLLW). The shoreline bank below elevation +14 ft MLLW would be designed as described in the removal action alternatives (with the same degree of improved aquatic habitat), but the elevation of the bank and T-117 Upland Study Area would be brought up to the final elevation of +18 to +21 ft MLLW. Restoring the T-117 Upland Study Area to the existing elevation would still meet the requirement for "unrestricted land use" and could support use for commercial redevelopment and/or public access. Option B, No backfilling of the T-117 Upland Study Area; transition directly to habitat creation, among other site improvements Under this option, a redevelopment project for the creation of aquatic habitat would be implemented immediately following the removal action. Habitat creation would be coordinated with EPA and Ecology to ensure that any newly created intertidal habitat (within the present T-117 Upland Study Area) would meet the sediment RAOs at the appropriate point of compliance. The completion design for Option B (as well as any later redevelopment action) would include provisions for long-term site stability (i.e., protection against erosion and the institution of protective covenants, as needed). The details on the design of the restoration plan are still being developed; therefore, the final site configuration is unknown. As the restoration design progresses, it will be coordinated with the NTCRA design to ensure that sediment and/or soil RvALs are being met. General cross sections of Options A and B are shown on Figure 7-7, along with the baseline completion approach, which was assumed for both removal action Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 233 alternatives for costing purposes. All of the completion options (i.e., Options A and B and the baseline completion option) will result in a site that is protective of human health and the environment and will meet the established RAOs. The selection of the appropriate completion option will be made at the time of remedial design based on the results of site-use evaluations. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 234 Slipsheet (8-1/2 x 11) Figure 7-7. Upland completion options Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 235 In the event that Option B is selected and can be integrated into the removal action design, existing upland areas that would be converted into intertidal areas would be further evaluated as part of the redevelopment project and in accordance with the sediment RAOsfor the sediment NTCRA. Upland soil that would underlie newly created aquatic areas and be located within the applicable depth of compliance would, at a minimum, need to meet the sediment RvALs set forth in Section 4. The large amount of excavation that will occur in the T-117 Upland Study Area under either removal action alternative will remove contaminants to levels estimated to be below the sediment RvALs at all upland locations, except one. This completion option would change the location of the shoreline and could increase the salinity of groundwater further inland. The large amount of excavation that will occur in the T-117 Upland Study Area under either removal action alternative will remove contaminants to levels estimated to be below the sediment RvALs at all upland locations, except one. A preliminary analysis of contaminant distributions in the upland soil indicates that areas where soil contaminant concentrations after excavation will be below the upland soil RvAL but not necessarily below sediment RvAL are limited to the area within the T-117 Upland Study Area on the west side near Dallas Avenue S. It is expected that this area would remain as upland subsurface soil and would not transition to exposed sediment if a habitat project were to be implemented. Furthermore, minor additional dredging and/or capping would be performed, as necessary, during the redevelopment project to ensure that soil beneath former upland areas that were newly converted to intertidal areas would meet RAOs for sediment. Site completion under all options would include site grading and the installation of stormwater features in the T-117 Upland Study Area and Adjacent Streets to facilitate upland stormwater management. The installation of these features on the T-117 Upland Study Area would require an easement for construction as well as ongoing maintenance. Furthermore, site completion under all options would provide for the necessary easement to re-establish the LDW power pole crossing at the site. This required easement is shown in a preliminary form in Figure 7-8Map 2-1. Final easement requirements will be determined during the NTCRA design phase. Regardless of how the removal action will be completed, the slope of the newly established shoreline will be designed to improve on existing habitat conditions and limit the potential for shoreline erosion. Either alternative or any completion option could influence the effectiveness of a hypothetical monitored natural recovery regime for LDW sediment in the vicinity of the T-117 EAA. These influences would be minimal because of the relatively small size of the T-117 Sediment Study Area (approximately 1.4 acres). The Alternative 1 baseline and completion option A would have little impact because these scenarios restore the shoreline and sediment to a topography similar to the existing configuration. Alternative 2 with completion option As would also restore the Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 236 shoreline topography. Although a cap would change the sediment grade, this would have little effect because of the size of the projected cap area relative to the LDW. Completion option B with either alternative would have a relatively larger impact because the shoreline and sediment grade would be changed. With this completion option it is likely that the area would become more depositional because the contouring for habitat would create depressions in the sediment and quiescent back water areas. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 237 8 Comparative Analysis of Removal Action Alternatives This section presents a comparative analysis of the two removal alternatives based on the criteria of implementability, effectiveness, and cost as defined in EPA's Guidance on Conducting Non-Time-Critical Removal Actions Under CERCLA (1993). The primary criteria to be considered are as follows: Implementability Technical feasibility and availability Administrative feasibility Effectiveness Overall protection of human health and the environment Achievement of RAOs Compliance with ARARs Reduction of toxicity, mobility, or volume through treatment Short-term effectiveness Long-term effectiveness and permanence Cost The discussion of removal action alternatives discussed in Section 7 serves as the basis for the comparative evaluation in this sSection. Throughout this discussion, the specific elements that make each alternative unique are noted (see the discussions entitled "Notable Differences"). As described in Section 7, both alternatives are presumed to include similar completion approaches (i.e., to elevation +14 ft MLLW). 8.1 IMPLEMENTABILITY This section discusses the three criteria that are important to the implementability of the alternatives. The successful implementation of both Alternatives 1 and 2 will depend to a large degree on the proper sequencing of removal work in the Adjacent Streets and Residential Yards, T-117 Upland Study Area, and the T-117 Sediment Study Area. Sequencing is discussed in Section 9.3.1. 8.1.1 Technical feasibility and availability 8.1.1.1 T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area Both alternatives are equal in terms of technical feasibility and availability for the T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area. Upland soil removal will be completed using commonly available construction Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 238 technologies and materials. Work in locations above the highest tide line in the LDW can be completed at any time because it will not be impacted by tidal fluctuations in the river. The upland work would preferably be conducted during the dry summer months to avoid potential construction and runoff problems associated with excessive rainfall. Excavated materials will be trucked offsite using conventional trucking equipment. Bank removal will be completed from the upland when the tides are out or with the use of an offshore barrier to isolate the inboard work area and facilitate access throughout the range of tide stages. Notable Differences None. 8.1.1.2 T-117 Sediment Study Area In the intertidal mudflat, sediment removal for Alternative 2 and the partial sediment removal and capping for Alternative 1 would be completed using commonly available upland construction equipment and materials. Excavated materials would be trucked offsite and imported material brought onsite using conventional trucking equipment. The work for both alternatives can be completed when the tides are out and it would be possible to best control the work being completed. The work would ideally be scheduled between May and August to maximize the number of days with the lowest tides. For submerged sediment within the removal boundary, the sediment removal for Alternative 2 and the capping for Alternative 1 would be completed using commonly available materials and floating construction equipment. Because of the relatively short duration of the project (20 to 35 days), it is not anticipated that other sediment cleanup projects being performed at the same time would have an adverse impact on the availability of the equipment necessary to perform the work. Dredged materials could be readily moved offsite and imported material brought onsite using conventional barges. The offloading of dredged sediment from barges to trucks or railcars for landfill delivery could be completed at existing facilities (e.g., another Port terminal). The work for both Alternatives 1 and 2 would need to be completed when tides are high to provide the needed draft for the floating equipment. Further constraints on available work time could be imposed by seasonal prohibitions on in-water work that have been established to protect certain fish species. The LDW fish window is the period of time when in-water work can be conducted, and this work must be coordinated with the tribes in advance. Typical fish windows for the LDW occur from October 1 to February 15 but can vary from year to year depending on the timing of the juvenile salmon out migration. Although in-water work can be accomplished in a manner that will accommodate these constraints (as demonstrated by other successful LDW projects), the overall project schedule may need to be lengthened to account for these seasonal interruptions. Arrangements will need to be made with the Marina to temporarily relocate some of the docks and floating structures in the proximity of the sediment removal area. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 239 Notable Differences Alternative 1 will result in a reduction in the cross-sectional channel area of the LDW, and a focused river hydraulics analysis will be needed to establish the impact (if any) of the capping on the channel cross section in the LDW. Alternative 1 would involve the removal of less sediment than would Alternative 2 and consequently would require 10 to 15 fewer low-tide days to complete. Both alternatives would result in the placement of import material (cap material under Alternative 1 and backfill under Alternative 2). This could affect the quality of clam habitat, and this effect could be more significant under Alternative 1 which would require erosion- resistant materials for the cap. For both alternatives, design details would be developed with a goal of limiting possible habitat impacts and accommodating fishing and clamming. The removal of less sediment under Alternative 1 also decreases the potential forfrequency of exceeding turbidity limits, so short-term risk is less for Alternative 1 than for Alternative 2. Map 7-3 shows the differences in the removal and capping areas between the two alternatives. 8.1.2 Administrative feasibility Administrative feasibility involves the activities needed to coordinate with other offices and agencies (e.g., obtaining permits for offsite activities or ROWs for construction). Very littleThe majority of the work for Alternatives 1 and 2 will be completed on land owned or controlled by parties other than the City and the Port., including the Port-owned offshore area of the Marina. Administrative requirements will include the need for the CityThe City will need to arrange for temporary road closures and/or special access arrangements within the Adjacent Streets and Residential Yards Study Area when removal in that study area is underway. Furthermore, access agreements will need to be established with property owners whose yards require excavation. As described in Section 7, institutional controls would be required under Alternative 1 to reduce the potential for the disturbance of the cap. These institutional controls would also require monitoring and maintenance. The details of the institutional controls would be developed in an institutional controls implementation plan during design, and the institutional controls would likely include proprietary controls (i.e., restrictive covenants); enforcement tools (i.e., agency orders requiring monitoring and maintenance); and informational devices (i.e., deed notice and state registry). Each of these controls is considered administratively feasible. None of the institutional controls would affect tribal treaty fishing rights. There are no apparent impediments to imposing restrictive covenants in order to provide long-term protection of the sediment cap areas because all of the affected tidelandInstitutional controls that would limit site disturbance of the sediment cap under Alternative 1 would be developed as part of the design process. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 240 The administrative feasibility of placing temporary barriers, such as berms or sheetpile walls, at or immediately offshore of the T-117 shoreline to facilitate bank removal will be addressed during removal action planning. Notable Differences Institutional controls (property deed restrictions, no-anchorage areas) would be required for the sediment cap under Alternative 1. Overall reliance on institutional controls, monitoring, and maintenance would be greater under Alternative 1. 8.1.3 Public involvement The Port, the City, and EPA will coordinate with the public on issues such as schedule, transportation plans, monitoring plans, permitting, and BMPs. The Port and the City will coordinate with EPA and stakeholders to hold meetings or otherwise provide information and receive input from stakeholders during the review of the EE/CA and subsequent design and removal action work. These activities will focus on issues of concern (e.g., truck traffic and control of the cleanup site, health and safety in the project vicinity, and protection of natural resources). 8.2 EFFECTIVENESS 8.2.1 Overall protection of human health and the environment Alternatives 1 and 2 are identical for the upland portion of the T-117 EAA and successfully meet the RvALs determined to be protective of human health and the environment. The alternatives will reduce long-term risks to human health and the environment by removing soil and sediment with COC concentrations greater than the selected RvALs, or containing any remaining contaminated sediment with an engineered aquatic cap. Both alternatives will achieve the RAOs and comply with all ARARs (Section 4 and Appendix G, respectively). The alternatives rely on removal and/or combined removal and /capping technologies, which are proven technologies that have been used successfully. Notable Differences Alternative 2 removes all of the sediment with COC concentrations that exceed the RvALs within the mudflat and submerged portions of the T-117 Sediment Study Area, and thus does not include a cap. ; whereas In contrast, Alternative 1 includes a combination of removal and capping, with the potential for the subsequent disturbance of the cap, which could expose underlying contamination. 8.2.2 Achievement of RAOs Both Alternatives 1 and 2 satisfy the RAOs for the T-117 EAA by creating a post removal condition that meets the site RvALs at the specified points of compliance. This is accomplished through the removal (Alternative 2) or a combination of the removal and effective long-term containment of sediment (Alternative 1). Notable Differences None. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 241 8.2.3 Compliance with ARARs and other requirements ARARs were discussed in Section 4. Both alternatives will meet the substantive requirements of ARARs. Both alternatives include the removal of contaminated soil to allow for a broad range of future land uses, including potential redevelopment as habitat, and are therefore equivalent in meeting ARARs pertaining to upland cleanup. For the sediment removal, the SQS is applicable to the T-117 Sediment Study Area and any areas where the cleanup or follow-on site development creates intertidal or subtidal areas. Completion of either alternative will result in COC concentrations that are well below the SQS because of the use of clean backfill or capping material. Compliance with the Endangered Species Act will be addressed in the biological assessment to be completed during the design phase of the NTCRA. The removal action is expected to be beneficial to threatened Chinook salmon because it greatly reduced their potential exposure to PCBs and other COCs. Under the assumed completion approach, the shoreline bank will be replaced at a grade that is less steep (e.g., 3H:1V) than the existing grade and will provide both long-term stability and improved habitat (i.e., natural sand and gravel substrate underlain by stabilizing layer of quarry spalls) with a small net increase (less than 0.1 ac) in aquatic habitat area.creage. Both alternatives will comply with TSCA because all soil and sediment with total PCB concentrations greater than 50 mg/kg will be designated for disposal at a TSCA landfill, as described in Section 4.3.1.2. The extent to which the ARARs are met by each alternative is summarized in Table 8-1. As presented in Table 8-1, the two alternatives are similar and meet the same substantive requirements. Notable Differences None. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 242 Table 8-1. Comparison of removal action alternatives relative to ARARs and other requirements TBC Compliance with ARARs and Other Requirements Regulatory Requirement Alternative 1 Alternative 2 ARARs The removal will comply with these requirements by meeting RvALs Washington State Model Toxics Control based on a broad range of possible future land uses and CULs protective Same as Alternative 1. Act (WAC 173-340-440) of upland terrestrial species in the upland areas Washington State Water Quality The removal action will comply with these regulations through the Standards for Surface Waters Same as Alternative 1. implementation of BMPs and a water quality monitoring program. (WAC 173-201A) Total PCB concentrations will be below the SQS for both alternatives Total PCB concentrations will be below the Washington State Sediment because of the combined action of removal and the use of clean capping SQS for both alternatives because of the Management Standards (WAC 173-204) material. Restrictive covenants and monitoring will be required for combined action of removal and the use of sediment caps to ensure long-term compliance. clean backfill material. The removal action will comply with TSCA because all soil and sediment Toxic Substances Control Act with total PCB concentrations greater than 50 mg/kg dw will be Same as Alternative 1. (40 CFR 761) designated for disposal at a TSCA landfill. Other Requirements TBC Federal Water Pollution Control Act/ The removal action will comply with these regulations through the Clean Water Act Same as Alternative 1. implementation of BMPs and a water quality monitoring program. (33 USC 1251-1376; 40 CFR 100-149) The removal action will comply with the substantive requirements of these Construction in State Waters, Hydraulic regulations by implementing BMPs for the protection of fish and shellfish, Same as Alternative 1. Code Rules (RCW 75.20; WAC 220-110) as recommended by the WDFW. Federal Endangered Species Act of The removal action will comply with the substantive requirements of the 1973, act by implementing BMPs for the protection of fish and shellfish, as Same as Alternative 1. 16 USC 1531 et seq. recommended by NMFS and USFWS. (50 CFR 200; 50 CFR 402) Essential Fish Habitat provisions of the The removal action will comply with the requirements of the act by Magnuson-Stevens Fishery Conservation implementing BMPs for the protection of EFH, as recommended by Same as Alternative 1. and Management Act NMFS, and respond in writing to NMFS's recommendations. (50 CFR 600) Table 8-1. Comparison of removal action alternatives and ARARs (cont.) Compliance with ARARs and Other Requirements Regulatory Requirement Alternative 1 Alternative 2 These substantive permit requirements are anticipated to be applicable to actions such These substantive permit requirements are anticipated to be applicable to as dredging, which may affect the Rivers and Harbors Appropriations Act actions such as dredging, which may affect the navigable portions of the navigable portions of the waterway. (33 USC 403; 33 CFR 322) waterway. Use of capping as a technology may require special review Sediment removal and restoration to and approval. existing grade (except at the Marina, where backfilling would not be done) is likely to meet these requirements. Solid Waste Handling Standards The removal project will comply with these standards. Same as Alternative 1. (WAC 173-350) Washington Dangerous Waste The removal action will comply. Same as Alternative1. Regulations (WAC 173-303) Shorelines Management Act (KCC The project will be planned and conducted to meet the substantive Same as Alternative 1. Title 25) requirements for shoreline management. ARAR applicable or relevant and appropriate KCC King County Code TSCA Toxic Substances Control Act requirement NMFS National Marine Fisheries Service USC US Code BMP best management practice PCB polychlorinated biphenyl USFWS US Fish and Wildlife Service CFR Code of Federal Regulations RCW Revised Code of Washington WAC Washington Administrative Code CUL cleanup level RvAL removal action level WDFW Washington State Department of Fish dw dry weight SQS sediment quality standards and Wildlife EFH essential fish habitat TBC to be considered Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 244 8.2.4 Reduction of toxicity, mobility, or volume through treatment Neither Alternative 1 nor Alternative 2 includes treatment technologies for reasons detailed in Section 6. Notable Differences None. 8.2.5 Short-term effectiveness and implementation risk 8.2.5.1 T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area Short-term effectiveness includes an assessment of risks associated with the implementation of the removal action (in contrast to long-term effectiveness, which considers the effectiveness of the action after completion). Short-term effectiveness can often be enhanced through the use of BMPs and appropriate planning, which will be developed during the design phase. The removal of impacted soil from the T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area has the potential for the short-term release of contaminated material to the river and surrounding areas (e.g., adjacent properties) if not properly planned and controlled. The highest concentrations of PCBs and other COCs are present in the upland soil, and precautions will be taken during the removal action to ensure that the LDW and the surrounding community will not be exposed to soil from the interior upland removal areas. Runoff controls and other safeguards similar to those used during the TCRA (RETEC 2007b) will be implemented under both removal alternatives. Soil will be removed from the shoreline bank under both alternatives, and safeguards will be used during this phase of the work, including engineering controls (i.e., completing the excavation during low tide, covering the excavated areas soon after they are exposed, and using berms or sheetpile walls to isolate the work area from the river). Such measures will greatly limit the potential for releases from the upland and upper shoreline work zones. The completion of the upland/bank excavation from the top of the shoreline berm to the intertidal area will ensure that any material released from the upper reaches of the cut during excavation will be captured as part of the other removal work in the lower portion of the bank (i.e., down to the intertidal mudflat elevation). Notable Differences None, (because the same removal action is identified for both Alternatives 1 and 2). 8.2.5.2 T-117 Sediment Study Area The disturbance of impacted sediment within the removal area will likely result in some short-term release of PCB-containing material to the immediate LDW vicinity of the LDW. Engineering controls (i.e., completing the excavation in the mudflat when the tide is low and covering the excavated face soon after it is exposed) may reduce the Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 245 release potential from this portion of the sediment removal area. Experience at other intertidal sediment remediation projects at the Hylebos Waterway (Section 7.1.3) has shown that by completing the excavation during low tide, the excavated face does not need to be covered soon after exposure in order to limit short- term releases. Scheduling the bank/mudflat soil removal during periods of very low tide during May through August will allow for the greatest amount of work to take place during days with very low tides, when the potential for sediment to be released as a result of contact with the rising tide is lowest. Alternative 1 involves a partial removal, all above elevation 0 ft MLLW; whereas Alternative 2 involves complete removal in the mudflat zone to a cut elevation as low as -2 ft MLLW. Consequently, Alternative 2 has a slightly higher risk of release because some of the excavation will may be completed in 1 to 2 ft of water near the edge of the mudflat excavation if berms or sheet pile walls are not used for the excavation. The removal of sediment from the submerged zone will be done using dredging equipment rather than upland-based equipment. Engineering controls (i.e., dredging and barge filling practices designed to limit turbidity) will limit the potential for releases from the submerged zone to the extent reasonably possible. Water quality monitoring will be conducted to verify that concentrations in the water column are within acceptable limits. Notable Differences Alternative 1 involves the capping of submerged sediment and does not include dredging in the submerged portion of the sediment removal area; Alternative 2 involves the complete removal in the submerged area. Thus, Alternative 2 has a higher potential for release during implementation because of the disturbance of submerged sediment by means ofduring dredging is typically greater than that associated with controlled capping. Differences between the two alternatives regarding the relative need for institutional controls is discussed in Section 8.2.6.2. Alternative 1 would require institutional controls for the in-water cap. 8.2.6 Long-term effectiveness and permanence 8.2.6.1 T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area Both Alternatives 1 and 2 involve the permanent removal of COC-contaminated material from the T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area to meet the specified RAOs. For these areas, both alternatives are equivalent in terms of potential long-term effectiveness and permanence. Notable Differences None. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 246 8.2.6.2 T-117 Sediment Study Area Alternative 1 relies on the long-term effectiveness of sediment capping at locations where this technology is used. Removal provides the greatest long-term reliability because contaminated sediment is removed and thus not available for potential release to LDW sediment in the future. Alternative 2 does not involve any significant in-water capping. However, under Alterative 2, a limited amount of sediment within the rock riprap along the toe of the Marina shoreline contains elevated PCBs (i.e., samples Trans- A-sed, Trans- B-sed, and 99-G, as shown on Map 2-8). Rather than removing the riprap and undermining the Marina shoreline, the sediment within the riprap may be removed (manually at low tide or by divers) or contained by a localized cover. The cap proposed for Alternative 1 would be designed to remain stable and provide long-term containment of the remaining impacted material beneath the capped areas. The T-117 Sediment Study Areacap would be located outside of the fFederally authorized navigation channel, which is is generally the area outside of areas of activity where ship traffic or prop wash could cause damage. However, vessel traffic outside of the navigation channel is not uncommon and could result in the disturbance of the cap. The long-term reliability of sediment caps would be augmented with institutional controls as described in Section 7, can be maintained that wouldincluding restrictive covenants and informational devices to limit the potential for cap disturbance, along with enforcement tools and enhanced through the implementation of in an operation, maintenance, and monitoring plan (OMMP) that would require periodic monitoring and maintenancerepair of the cap as well as adaptive management, if necessary. The cap's performance would be monitored to ensure long-term containment and the protection of human health and the environment. EPA typically requires that a cap's performance be assessed at least once every 5 years for as long as deemed necessary Monitoring a cap's performance will be regularly required as specified in an EPA- approved OMMP to ensure the long-term containment of contaminants beneath the cap. to ensure the long-term containment of contaminated sediment remaining on site beneath the cap. Ecology has similar monitoring and periodic review requirements set forth under MTCA (WAC 173-340-410 and 420) that must be considered as an ARAR for Alternative 1. Additional discussion of long-term cap monitoring is included in Section 9.3.3. Notable Differences The lLong-term effectiveness and permanence reliability of Alternative 1 depends on continued integrity and performance of the sediment cap, which would also require institutional control to ensure long-term effectiveness and permanence. Alternative 2 does not include capping, so it has a greater degree of permanence and long-term effectiveness without reliance on institutional controls. Thus, Alternative 1 has a higher potential of future release of COCs as compared to Alternative 2. This potential is associated with the possibility of disturbance of the Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 247 cap. However, this potential is considered small for Alternative 1 and would be minimized and managed through cap design elements, institutional controls, monitoring, and maintenance as needed. Finally, Alternative 2 also allows for maximum design flexibility in that the final site contours can be designed without the need to accommodate permanent intertidal cap structures. This will be particularly advantageous in locations where habitat redevelopment or other final site uses will be selected and implemented in cooperation with the South Park Community. 8.2.6.3 Magnitude of risk Upon completion, Alternative 1 would have a slightly higher magnitude of risk than would Alternative 2. This higher risk is associated with the relatively large portion of contaminated sediment that would remain in place, isolated beneath the sediment cap, in the T-117 Sediment Study Area. Applicable design guidance would be used in the design of the cap if Alternative 1 were to be selected, but the cap would need to be closely monitored to ensure its integrity and performance. Cap integrity and maintenance would also need to rely, in part, on the institutional controls that have been described previously in this EE/CA. The extent to which some of these controls are implemented and maintained, and their effectiveness over the life of the remedy, could contribute to the relative future risk associated with the capping option. In contrast, Alternative 2 will have a slightly lower magnitude of risk because all of the contaminated sediments will be removed and a cap will not be needed to isolate material that would otherwise remain in place. Both alternatives have the same estimated magnitude of risk for the upland areas of the T-117 EAA because the removal actions proposed for those areas will be the same. Notable Differences The relative magnitude of risk associated with Alternative 2 is slightly higher than that for Alternative 1. This is higher risk would result from contaminants and residuals that would still remain beneath the sediment cap located within the LDW after completion of the NTCRA. 8.3 COST The estimated costs for Alternatives 1 and 2 are summarized in Table 8-2. These costs are based on present value20 and include long-term monitoring and maintenance costs.21 When long-term monitoring and maintenance costs are considered, the cost difference between Alternatives 1 and 2 is $1.5 million. 20 Present net worth analysis based on 2008 year 0, and 5% net discount rate. 21 Long-term monitoring costs based on four events over 10 years. Maintenance costs were assumed to have a present value of one-fourth the construction cost of the cap. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 248 Table 8-2. Comparison of costs for Alternatives 1 and 2 a Estimated Cost Component Alternative 1 Alternative 2 Capital costs $14,790173,000 $15,236860,000 Contingencies, design, management and oversight $14,016620,000 $154,280679,000 Long-term monitoring and maintenance $430,000 $100,000 Sales tax $1,89031,000 $1,910854,000 Total estimated cost (rounded) $310,7400,000 $331,2900,000 a Present net worth analysis based on 2008 year 0, and 5% net discount rate. 8.4 SUMMARY OF COMPARATIVE ANALYSIS In summary, Alternatives 1 and 2 are similar in their implementability and effectiveness. The estimated cost for Alternative 1 is slightly less than that for Alternative 2, although the c.osts for both alternatives are considered to be relatively high relative to other sites where less-restrictive RAOs are required and a broader range of lower-cost alternatives are considered appropriate. Alternative 2 offers the advantage of the increased removal of COCs from the T-117 Sediment Study Area without reliance on capping, but has slightly more significant short-term water quality impacts during excavation and dredging and a slightly higher overall cost than does Alternative 1. Alternative 1 offers the advantage of a lower potential for short-term releases because of the lower volume of sediment removed, less reliance on over-water dredging, and lower initial cost. However, Alternative 1 also has a slightly higher potential of long-term contaminant release from the capped areas and higher longterm costs associated with cap monitoring and adaptive management, if necessary. Table 8-3 provides a summary comparison of the two removal action alternatives. Removal volumes are listed, together with summary comments on the comparative criteria discussed in Section 8.2. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 249 Table 8-3. Summary of comparative analysis Ability to Meet RAOs Component Alternative 1 Alternative 2 Protection of human health Alternative is protective. Alternative is protective. and the environment a a Achievement of RAOs RAOs are achieved. RAOs are achieved. ARARs Alternative complies with ARARs. Alternative complies with ARARs. Effectiveness Alternative is effective and permanent. Alternative is effective and permanent. Long-term effectiveness and Removes contaminated soil from the T-117 Upland Study Area permanence and Adjacent Streets and Residential Yards Study Area. Removes contaminated soil from the T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area. Sediment cap requires long-term monitoring and maintenance. Upland removal: Contaminated soil excavated under tightly controlled conditions, greatly reducing the short-term potential Upland removal: Contaminated soil excavated under tightly for release to surrounding areas or the LDW. controlled conditions, greatly reducing the short-term potential Sediment removal: Completed from upland during low tides as for release to surrounding areas or the LDW. feasible to reduce risk of COC releases to LDW. Alternative Sediment removal: Completed from upland during low tides to does not involve excavation in water because upland excavation reduce risk of COC releases to LDW. Alternative involves some Short-term effectiveness will not go deeper than 0 ft MLLW contour. upland-based excavation in the water close to the existing 0 ft Alternative 1 involves dredging of about 35% of the dredged MLLW contour. volume estimated for Alternative 2. Short-term impacts to water Alternative 2 involves more extensive submerged zone dredging quality will be of slightly shorter duration as compared with those than does Alternative 1. Short-term impacts to water quality will for Alternative 2. Short-term impacts to water quality will be be managed through engineering controls and BMPs. managed through engineering controls and BMPs. Implementability Upland soil removal under both alternatives can be readily Upland soil removal under both alternatives can be readily implemented with proper site preparation and water implemented with proper site preparation and water management measures in place. Shoring and barriers will need management measures in place. Shoring and barriers will need Upland removal to be included in the removal design to ensure upland to be included in the removal design to ensure upland remediation areas are not inundated by the river and deeper remediation areas are not inundated by the river and deeper excavations can be completed with stable side walls. excavations can be completed with stable side walls. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 250 Ability to Meet RAOs Component Alternative 1 Alternative 2 Intertidal bank and mudflat work is best completed in May through August when very low tides occur. Alternative 1 does not involve any upland-based sediment Intertidal bank and /mudflat work is best completed in May removal below elevation 0 ft MLLW and is easier to implement through August when very low tides occur. than Alternative 2. Alternative 2 involves some upland-based sediment excavation Work is completed with conventional upland and waterwayin the water at the existing 0 ft MLLW contour (2 ft deep to based equipment. Sediment removal elevation -2 ft MLLW) and is more difficult to implement than Alternative 1 involves mudflat and submerged zone capping that Alternative 1. will result in a slight decrease of the cross-sectional area of the Work is completed with conventional upland and waterway- LDW. based equipment. Work will be completed on land owned or controlled by the Port. Work will be completed on land owned or controlled by the Port. There are no apparent impediments to imposing restrictive covenants to provide long-term protection of the capped area because all of the affected land is controlled by the Port. b Cost $310,7400,000 $331,2900,000 a RAOs: Human health seafood consumption. Reduce human health risks associated with the consumption of resident LDW fish and shellfish by reducing sediment and surface water COC concentrations to protective levels. Human health direct contact. Reduce human health risks associated with exposure to COCs through direct contact with sediments and incidental sediment ingestion by reducing sediment concentrations of COCs to protective levels. Ecological health benthic. Reduce toxicity to benthic invertebrates by reducing sediment COC concentrations to comply with SMS. Ecological health seafood consumption. Reduce risks to crabs, fish, birds, and mammals from exposure to COCs by reducing concentrations of COCs in sediment and surface water to protective levels. Sediment Protection. Reduce PCB concentrations in upland soils to ensure protection of sediments. a Volumes of PCBs removed are estimates. b Includes the baseline completion approach. Costs are life- cycle costs. For details see Appendix J. ARAR applicable or relevant and appropriate requirement PCB polychlorinated biphenyl BMP best management practice Port Port of Seattle COC contaminant of concern RAO removal action objective LDW Lower Duwamish Waterway SMS Washington State Sediment Management Standards MLLW mean lower low water T-117 Terminal 11-7 Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 251 9 Recommended Removal Action Alternatives and Implementation This section presents the conclusions for the EE/CA and discusses: The recommended removal action alternative The EE/CA recommends Alternative 2 for the T-117 NTCRA. Removal action sequencing and schedule The sequencing, which is proposed to start in the Sediment Study Area and progress upland, finishing with the cleanup of the Adjacent Streets and Residential Yards. The cleanup implementation is anticipated to begin in 2012. NTCRA work plan development The work plan will be provided as part of the T-117 NTCRA design. Long-term operation, maintenance, and monitoring planOMMP The OMMP will be developed during the T-117 NTCRA design. 9.1 RECOMMENDED REMOVAL ACTION ALTERNATIVE The recommended alternative for the T-117 NTCRA is Alternative 2. The key advantage of Alternative 2 is that it provides for maximum long-term effectiveness and permanence. Although Alternative 2 would cost slightly more to implement because of the added quantity of dredged material, this addition cost will be offset in part by the elimination of lower post-NTCRA cap monitoring and performance review costs that would be required under Alternative 1. Both alternatives have the potential for short-term impacts associated with the release of COCs from the disturbance of contaminated sediment during either dredging or capping. Alternative 2 also has the greater potential for the disturbance of contaminated sediment because it involves more dredging, which increases greater short-term impacts, associated with additional dredging, ande dredging disturbs more sediment than does capping. In either case, but these short-term impacts of capping and dredging can be reducedmitigated through the use of proper BMPsdredging project design and controls. Because Alternative 2 does not involve capping, it does not require institutional controls to protect the sediment. Institutional controls would be required under Alternative 1 to reduce the potential disturbance of the cap. These institutional controls would also require monitoring and maintenance. While Alternative 1 has a higher potential for the future release of COCs compared with Alternative 2, this potential is considered small and would be limited and managed through appropriate cap design, institutional controls, monitoring, and maintenance, if needed. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 252 Alternative 2 also allows for maximum design flexibility because final site contours can be designed without the need to accommodate permanent intertidal cap , which structures. This will be particularly advantageous in locations where habitat redevelopment or other final site uses areto be selected and implemented in cooperation with the South Park Community. Final site contours can be designed without the need to accommodate permanent intertidal cap structures. Under Alternative 2, A limited amount of sediment located within the spaces between the rock riprap along the toe of the Marina shoreline contains elevated concentrations of PCBs. Rather than removing the rip rap and undermining the Marina shoreline, the sediment within the rip rap may be removed and/or contained by a localized cover. capping would be limited to only those locations where dredging is not feasible (e.g., around the base of intertidal structures). Alternative 2: Is protective of human health and the environment Achieves the site-specific RAOs Complies with ARARs Provides long-term effectiveness through the removal of the majority of contaminant mass at the site Is feasible and relies on technologies that are readily available Monitoring and maintenance of the T-117 Sediment Study Area will be a part of the post-NTCRA activities. 9.2 REMOVAL ACTION SEQUENCING AND SCHEDULE 9.2.1 Sequencing The successful implementation of the removal action will depend to a large degree on the sequencing of removal work in the T-117 Upland Study Area, the Adjacent Streets and Residential Yards Study Area, and the T-117 Sediment Study Area. An example of project sequencing is provided in Table 9-1. Other sequencing approaches that do not require a barrier wall may be considered during the design stage of the project. Sequencing within the T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area will take into consideration access logistics, potential traffic impacts on the surrounding community, and the limited availability of soil and sediment staging areas. Remedy implementation and the scheduling of in-water construction activities will be coordinated with the tribes to minimize impacts on tribal fishing. Proper sequencing within the T-117 Sediment Study Area will involve the removal of the most highly contaminated sediment first in order to eliminate the potential for recontamination of the remaining sediment areas. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 253 Table 9-1. Example NTCRA sequencing overview for primary construction tasks Step Task Benefits Issues No aquatic impacts to be mitigated No in- May require pre-excavation as a water work permit required result of the presence of debris Install barrier wall No in-water work window schedule Will likely require steel Z-piles 1 in vicinity of top constraints of bank Will likely require interim No net loss of aquatic habitat groundwater control, treatment, Ability to control groundwater discharge and discharge during upland activities No aquatic impacts to be mitigated No in- water work permit required No in-water work window schedule Capping of sediment under Excavate bank constraints Alternative 1 should immediately and intertidal 2 Bank excavation before sediment dredging follow the bank/mudflat mudflat from greatly reduces sediment recontamination excavation (e.g., same tidal upland at low tide potential cycle). Excavation allows for better removal along piles than dredging Dredging sediment prior to upland excavation means upland is still in place to provide a location for sediment staging, if Capping of sediment under needed Alternative 1 2 should Upland source controlled by piles, immediately follow the 3 Dredge sediment groundwater control bank/mudflat excavation or May be able to use groundwater treatment dredging (e.g., same tidal system for dewatering sediment, if required cycle).. Limits amount of work under in-water work window Control of upland impacts Removal of contaminants and physical containmentControl orf upland control of contaminant pathways to sediment allows Will require appropriate security schedule flexibility so the upland cleanup and access control if upland left can be coordinated with and habitat as an open excavation behind restoration to be coordinated if appropriate Excavate T-117 the sheetpile wall or similar mitigation agreements are in place 4 Upland Removal barrier Sheetpile wall or similar barrier may be left in Area Groundwater control, treatment place after cleanup without creating net loss and discharge may continue to of aquatic habitat be required until piles are Habitat design flexibility is maintained by removed allowing re-grading behind sheetpile wall or similar barrier Barrier wall limits potential for releases during construction Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 254 Step Task Benefits Issues Existing stormwater controls could stay in place until all sediment and upland excavation is complete Dallas Avenue S excavation could be coordinated with the adjacent excavation in the T-117 Upland Study Area Requires stormwater controls to Excavate Adjacent Streets excavation could be be implemented during the Adjacent Streets coordinated with soil removal if required in 5 excavation of the Adjacent and Residential the Residential Yards Streets and Residential Yards Yards Study Area Stormwater drainage could be incorporated Study Area into the final completion of the T-117 Upland Study Area Because this study area has less contaminated material, it will be cleaned up last to prevent recontamination from the cleanup activities at other study areas T-117 Terminal 117 The following is a detailed example of how the project work could progress and demonstrates how the actions could be implemented in phases. It is assumed that the work would progress according to the general order of primary construction tasks outlined in Table 9-1. 1. Relocate marina docks as needed to allow access for sediment removal and undertake environmental surveys of T-117 EAA study area buildings (for asbestos and lead paint) as may be needed prior to demolition. 2. Establish traffic control measures within the site and for safe access to and from the site. 3. Abandon all onsite wells located within the study areas. 4. Construct temporary decontamination and work areas for demolition of T-117 EAA structures. 5. Establish and monitor perimeter controls. 6. Protect catch basin inlets and provide drainage control as needed for demolition. 7. Demolish and remove T-117 EAA buildings and other above-ground structures to prepare for soil removal. 8. Re-establish work and decontamination areas, as necessary, to make effective use of new areas within the T-117 Upland Study Area formerly occupied by buildings. 9. Remove known subsurface features within the T-117 Upland Study Area as needed to facilitate subsequent large-scale soil removal (e.g., USTs, remnant utility corridors, and building foundations and floor slabs from removed Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 255 structures) and re-stabilize removal areas using temporary backfill, paving, or other appropriate measures. 10. Re-evaluate site drainage and enhance as needed to ensure proper controls and treatment. 11. Construct soil and sediment staging areas and establish surface drainage controls (i.e., stormwater diversion, interception, and treatment) for the first stage of soil removal. 12. Establish vehicle loading and wheel wash facilities. Implement monitoring required for soil removal activities. 13. Install sheetpile wall, as needed, along the top of the shoreline bank. Install barriers and groundwater controls (dewatering or subsurface barriers) as needed to protect the LDW and limit or divert groundwater influx during bank and sediment removal work. 14. Excavate soil from the bank and adjacent intertidal mudflat. Load soil into haul trucks for offsite disposal at Subtitle D or C landfill in stages in order to ensure a controlled and manageable removal process. 15. Adjust and relocate site controls, drainage collection and treatment facilities, and staging areas for next phase of soil and sediment removal. 16. Implement additional measures as needed to ensure stability and proper drainage controls within the T-117 Upland Study Area (grading, planting, and paving). 17. Construct temporary sediment receiving and staging facilities for in-water dredging operations, if needed. Dredge sediment within the T-117 Sediment Study Area and backfill as required. Conduct monitoring as required during dredging to ensure compliance with specified water quality parameters and proper positioning of the dredge. Transport dredged sediment directly to the upland area or transport sediment by barge to an onsite or offsite transfer/loading facility for subsequent loading into haul trucks or rail cars for disposal at Subtitle D or C landfill. Dismantle and restore upland sediment staging areas and associated facilities upon completion of dredging. 18. Install subsurface soil dewatering systems (e.g., hydraulic barriers, well-point system) in close proximity of deep inland (non-shoreline) soil removal prisms for the removal of groundwater, establish onsite storage and treatment for extracted groundwater, and dewater the excavated areas (details regarding the extent to which these prisms are dewatered and excavated at once or in stages will be set forth in the detailed project plans). 19. Excavate soil from removal prisms located above the water table in phases. Load soil into haul trucks for offsite disposal at Subtitle D or C landfill, and Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 256 grade and/or provide temporary covers and drainage controls (as needed) to stabilize removal areas, particularly those located along the shoreline bank. Adjust staging areas and drainage controls as needed to accommodate subsequent soil removal phases and ensure continued control of site runoff. 20. Excavate deep inland soil removal prisms and backfill to above the water table as necessary to provide proper drainage, allow continued site access, and reduce the accumulation of rainwater in isolated removal prisms. Load soil into haul trucks for offsite disposal at Subtitle D or C landfill. 21. Conduct soil removal in Adjacent Streets and Residential Yards in stages and in accordance with detailed project plans and with agreements with affected property owners. Modify street access controls as removal progresses within the street alignments to limit the impacts on residential access. 22. Construct new stormwater infrastructure. 23. Conduct monitoring and control dust and runoff during soil removal to ensure protection of the public and prevent recontamination of adjacent areas. Restore streets and yards and install improved drainage collection and treatment facilities. 24. Install long-term monitoring wells as needed to monitor post-removal performance. For this example, it was assumed that the T-117 Upland Study Area would be completed to a minimum elevation at or above +14 MLLW in accordance with the baseline completion option. Alternate completion options, such as those described in Section 7.3 and Figure 7-7, could require slightly different phasing and backfilling approaches for the upland soil and near-shore sediment removal activities. 9.2.2 Schedule The following schedule elements are based on the T-117 EE/CA SOW: 2010 EE/CA is approved, and EPA issues an amended Action Memorandum. NTCRA design process is initiated. 2011 Consent Order issued to respondents. 2012 to 2013 NTCRA design and work plans are completed. NTCRA is implemented. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 257 2013 to 2014 Site re-development (e.g., habitat restoration) is initiated. The This draft final final EE/CA will be submittedis for public comment. within 30 days of receipt of EPA comments on the interim draft final EE/CA. The public comment period is 60 days. The final EE/CA will be published within 30 days after EPA's EPA will prepare publication of their a responsiveness summary based on public comments and issue an amended Action Memorandum for the T-117 EAA NTCRA, which will replace the Action Memorandum issued on July 22, 2005. This Action Memorandum will be issued no later than September 30, 2010. The initial NTCRA design package will be prepared and submitted to EPA within 1 year (2011) after EPA issues an the amended Action Memorandum. based on an approved EE/CA (i.e., sometime in 2011) and will likely be finalized sometime in 2012. The implementation of the NTCRA will begin the following year (20132012) after EPA has approved the design package. Timing of the EE/CA, the design phase, and NTCRA implementation may be adjusted, if necessary, to accommodate a selected site completion option (see Section 7.3). External factors, such as coordination with other LDW projects, the South Park Bridge replacement, weather, and salmon migration may also affect the NTCRA implementation schedule. Typical fish windows for the LDW occur from October 1 to February 15 but can vary from year to year depending on the timing of the juvenile salmon out- migration. Activities that occur after completion of the EE/CA are not part of the current ASAOC and are subject to revision in accordance with the negotiated Consent Order with EPAnext agreement. 9.3 NTCRA WORK PLAN DEVELOPMENT The work plan for the 2006 TCRA (RETEC 2006) will serve as a starting point for the NTCRA work plan and will be modified and augmented as needed to address the requirements set forth in the eventual NTCRA SOW. The TCRA work plan included health and safety procedures; routine inspection, maintenance, and monitoring tasks, such as cap inspection and maintenance, stormwater system maintenance, soil handling procedures, notification requirements, groundwater monitoring procedures and other performance standards directly applicable to the T-117 EAA and the NTCRA project. Several of the key elements of the NTCRA work plan are discussed in the following subsections. 9.3.1 Health and Safety A detailed HSP will be prepared for the NTCRA and will be applicable to all site workers, as well as those providing oversight. The plan will also address controls and safety measures designed to protect personnel and nearby residents. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 258 9.3.2 Site Controls The NTCRA work plan will specify temporary erosion and sediment controls for all aspects of the construction work, including excavation, and soil or sediment stockpiling in the truck loading areas. Erosion control measures and controls for stormwater will be developed according to guidance contained in Ecology's Stormwater Management Manual for Western Washington (Ecology 2005b) and the King County, Washington, Surface Water Design Manual (King County 2009). Particular emphasis will be placed on control measures that prevent the offsite transport of contaminated materials (e.g., truck wheel washes, stormwater controls, and dust controls). The NTCRA work plan will include a schedule for the inspection and maintenance of these controls during all applicable phases of the project. Noise monitoring and abatement criteria and procedures will also be specified. The NTCRA work plan will also include procedures for air quality and meteorological monitoring similar to those used for the TCRA to ensure that potential airborne contaminants are monitored so that they can be sufficiently controlled. Excavation, grading, and capping activities will be carried out in a manner that minimizes dust and the emission of odor (i.e., fugitive emissions). Stockpiles will be covered when there is no loading or unloading activityto the extent practicable to further minimize dust during construction. Water trucks will be used to control site dust, as necessary. 9.3.3 Performance mMonitoring The NTCRA remedial design work plan will include, but not be limited to, a sampling and analysis plan that specifies the sampling objectives and methods to be used for verification that soil and sediment above the RvALs have been removed. The plan will include a schedule of samples to be obtained, as well as a map indicating appropriate sampling locations within the T-117 EAA study areas. 9.3.3.1 Post-dredging verification sampling Post-dredging verification sampling will be performed at locations where sediment has been removed as part of the NTCRA. The purpose of this sampling will be to augment existing data and document that sufficient sediment has been removed to meet RvALs where no capping or fill is anticipated. Sampling will include surface samples to document that acceptable target COC concentrations have been achieved throughout the depth of compliance. At locations where capping or filling is anticipated, surface sediment samples will be collected prior to the placement of new material in order to establish pre-cap placement COC concentrations. These data will be used to evaluate the results of subsequent long-term cap/removal area recontamination monitoring. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 259 9.3.3.2 Soil excavation and sidewall verification sampling Verification sampling of excavation sidewalls and bottoms will be performed as part of the NTCRA to confirm that the COC concentrations that remain at the boundary of the removal areas are below the soil RvALs. It is anticipated that for the T-117 Upland Study Area excavation samples will consist primarily of composites from each sidewall and bottom of pre-designated removal areas. Verification sampling in the Adjacent Streets and Residential Yards Study Area will be limited to bottom samples because horizontal boundaries have been set by the MIS sampling method per agreement with EPA. In some cases, additional sampling of adjoining areas (e.g., un-sampled portions of yards adjacent to portions of yards being excavated) may be required. If sampling results indicate that soil at the vertical limit of excavation contains PCBs and dioxins and furans at concentrations that exceed their respective RvALs, additional excavation will be performed up to the full depth of compliance (i.e., 15 ft). At locations where removal did not extend to the full depth of compliance , additional excavation may be performed if the verification sampling results indicate that remaining soil contains PCBs and dioxins and furans target COCs at concentrations that exceed their respective RvALs. 9.3.3.3 Material specifications and construction QA/QC The NTCRA work plan will include detailed specifications for all material placed onsite, including imported structural fill; seed beds; gravel; material placed under asphalt, concrete, or roads; backfill for yards or upland soil or sediment landscaped areas with no structural featuresnon-structural areas; and sediment cap materials. There will be no caps in the Adjacent Streets and Residential Yards, caps will be use only in the sediment areas or upland areas that may become sediment. Specifications will include compaction rates, material size, and specific product types. A construction QA/QC plan that describes how construction procedures and material specifications will be verified, as well as any material testing that may be required following placement of construction components will be prepared for the T-117 NTCRA. 9.3.3.4 Monitoring of dredging activities Monitoring will be conducted during dredging activities and will include periodic turbidity measurements at upstream and down-current locations required by the water quality certification, as well as visual observations for floating debris and sheens. Periodic depth soundings will be conducted to ensure that the dredging is removing the designated material without excessive over-dredging. Response actions will be described in the NTCRA project plans. 9.45 ADDITIONAL INFORMATION NEEDS This section identifies additional data and information needss to be considered before implementation of the removal action. These additional needs are summarized in Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 260 Table 9-2. This information will be ,evaluated during the design phase, and incorporated in the design report. Activities needed to ensure that the removal action is being conducted in accordance with the removal action work plans and design and that the sRAOs are being met were described in Section 9.3. Post-removal action monitoring to evaluate the long-term effectiveness of the removal action and inspect for potential recontamination is described in Section 9.5. Table 9-21. Supplementary information needed to support the removal action design Information Need Rationale Design Additional Streets and Yards Study Area Information Assess groundwater quality in portions of the Adjacent Streets and Additional gGroundwater quality data Yards Study Area and provide better hydraulic gradient information Determine horizontal extent of removal areas at some yard Soil conditions locations. Determine vertical extent of soil removal in yards. Additional RAA Information Further assess recontamination potential to post-removal Additional groundwater monitoring downgradient areas Storm solids quality in the Marina catch Further assess recontamination potential. basins Marina NPDES stormwater discharge data Further assess recontamination potential. Map of Marina stormwater system and Further assess recontamination potential. drainage basins Additional Groundwater and Geotechnical Information Additional hydraulic conductivity and pump Needed for dewatering system design, if necessary, and posttest data removal recontamination assessment. Additional groundwater monitoringd and As needed to support design and post-NTCRA sediment horizontal and vertical gradient information recontamination evaluations Limited pre-design tidal study As needed to supplement existing tidal study data Geotechnical boring datas As needed to support design Sources of shoreline seeps and possible As needed to address active seeps in the removal action design control options, if needed Refinement of excavation prism Identify potential locations for supplementary pre-design sampling, Excavation prism data as needed. Site Preparation and Constraints Hazardous materials assessment Needed prior to demolition of T-117 Upland buildings. (e.g., lead paint and asbestos survey) Mapping of subsurface debris and Determine locations of former foundations, buried concrete, septic /obstructions tank, and backfill areas that might hinder excavation. Utility locate Identify current utility information. SCL tower location and /design Integrate with removal action activities and site completion design. SPU sStormwater discharge location and Integrate with removal action activities and site com pletion design. design Marina dock design To facilitate temporary relocation during sediment removal action. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 261 Information Need Rationale Coordination of Final Grade for Site Restoration TransitionHabitat Conceptual restoration grading plan Integration of final land use (e.g., habitat) with removal action Community Development of community protective Minimize exposure of residents. measures NPDES National Pollutant Discharge Elimination System NTCRA non-time-critical removal action RAA recontamination assessment area SCL Seattle City Light SPU Seattle Public Utilities T-117 Terminal 117 9.4.1 Additional Streets and Yards Study Area iInformation Additional information regarding groundwater beneath the Adjacent Streets and Residential Yards is needed in order to better assess groundwater quality and provide a baseline understanding of the hydraulic gradients and groundwater flow directions in portions of the Streets and Yards Study Area. The number and location of additional pre-design groundwater monitoring wells to be installed and monitoring to be conducted to verify that groundwater beneath this study area is not impacted will be evaluated in the design phase. Additional soil sampling in yards will be conducted during the design phase. Some yard areas that have not been sampled and are adjacent to DUs identified for removal will be sampled to define the extent of removal. Sampling to determine the vertical extent of removal in yards is also anticipated prior to removal. 9.4.2 Additional RAA iInformation Additional groundwater monitoring is planned in order to further assess the potential for groundwater from these two properties to contribute to recontamination. Data necessary to assess some of the pathways are limited. The adequacy of the upgradient and downgradient monitoring well network in the vicinity of the Basin Oil property will be reviewed and, if necessary, an additional well will be installed to evaluate groundwater quality associated with that EAA. Additional monitoring wells may also be needed to assess groundwater flow directions near the boundary between T-117 Upland Study Area and the Marina. This is primarily a post- NTCRA consideration, but monitoring wells can be installed during the design phase to provide useful information. Section 5.2.1.3 described the need for additional information regarding the Marina storm drain system in order to fully evaluate the potential for sediment recontamination. A map of the Marina storm drain system and a new outfall to the LDW were identified during a recent site visit. This additional information will be Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 262 used to assess the potential for the transport of COCs from the Marina to the T-117 Sediment Study Area. If it is concluded that the stormwater pathway poses a risk of sediment recontamination, then additional stormwater controls and/or monitoring will be required. These will be developed in cooperation with the Marina owner and in consultation with Ecology. 9.4.3 Additional gGroundwater and gGeotechnical iInformation Groundwater monitoring to date has focused on groundwater quality, observations of non-aqueous-phase liquid and calculations of groundwater flow direction. Prior to the design of the removal action, pump tests will likely be performed in select wells in order to estimate hydraulic conductivity. This information could be useful in the design of dewatering systems asthat may be needed to allow for deep excavation during soil removal. Several additional pairs of groundwater monitoring wells may be installed to measure vertical groundwater gradients at select locations within the site. These well pairs include one deep well and one shallow well. The difference in observed water levels in each well provides an indication of upward or downward groundwater gradients between the two depths at which the wells are screened. The methods and results of tidal studies already completed at the site will be reviewed to determine the extent to which they meet data needs for the removal action design. If data gaps that cannot be addressed by the above-described pump tests, are noted, a limited pre-design tidal study will be performed using select wells within the expanded monitoring well network to supplement the understanding of hydraulic conductivity across portions of the site. The methods and data quality objectives for the study will be included in a work plan to be submitted to EPA for approval prior to implementation. The removal action designers may require additional geotechnical information to assess soil conditions relative to excavation, shoring, or final site grades. Should this need arise, geotechnical borings will be advanced at locations within the EAA, either as a stand-alone field task or in coordination with the installation of monitoring wells or other subsurface work (e.g., additional soil sampling). The possible sources and, if needed, control methods for shoreline seeps will also be addressed during the remedial design phase. 9.4.4 Refinement of eExcavation pPrisms The proposed T-117 Upland Study Area soil removal prisms are discussed and presented in Section 7.1.2. As noted therein, the locations and depths of these prisms will be refined during final design and execution The existing removal prisms will be reviewed during the removal action design to identify locations where there may be uncertainty regarding the required extent of removal. Those locations where additional pre-design sampling is needed to refine the depth and/or lateral extent of Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 263 soil removal will be identified. A work plan for addressing soil removal data gaps will be prepared and submitted to EPA for review prior to implementation. 9.4.5 Site pPreparation and cConstraints Table 9-2 identifies a number of information needs necessary to provide the level of detail needed for final removal action design. Remaining structures within the T-117 Upland Study Area will need to be demolished and removed prior to excavation. A hazardous materials assessment will be needed to ensure that this work includes the abatement of any hazardous materials that may be present in these structures (e.g., asbestos or lead paint). Known subsurface structures and utilities will also need to be identified and shown on project drawings. These include the former utility corridors, underground tanks, septic tank, former building foundations, backfill areas, gas and water lines, electrical lines, and other features and utilities that may need to be protected or will require special methods for removal and disposal. Several design constraints will need to be addressed in the removal action and site completion designs. The first is the foundation and easement for restoration and maintenance of the western tower of Seattle City Light's high- voltage cable span across the LDW. The required easement and tower location and design will need to be identified so they can be integrated into the overall removal action design. The other design constraint involves SPU's plans to restore stormwater discharge to the LDW from a limited portion of the Streets and Yards Study Area through an outfall to be located somewhere within the T-117 EAA shoreline. The outfall location will need to be specified together with the appropriate outfall design in coordination with the eventual site completion design., This will ensure that the outfall can be integrated into the overall removal action and site completion. Information on the Marina's dock design and an access agreement with the Marina will also be needed to facilitate the planning for temporary dock relocation and subsequent restoration before and after sediment removal in the marina vicinity. 9.4.6 Coordination of final grade for site restoration transitionhabitat The NTCRA will be coordinated with known future site use concepts for the restoration of the T-117 EAA after completion of the soil and sediment removal activities. Available information on the final site configurations will be considered in the development of final site grades. If no site configuration is selected in time for the removal action design, then the site will be restored to the baseline completion grade. 9.54 LONG-TERM OPERATION, MAINTENANCE, AND MONITORING PLAN Post-NTCRA conditions at the T-117 EAA will be monitored and maintained to ensure that the RAOs and RvALs are being met, there is compliance with ARARs, and the remedy continues to be protective of human health and the environment. A long-term OMMP will be prepared in accordance with appropriate guidance documents WAC Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 264 173-340-410 during the design phase of the NTCRA and will address the final site configuration, site uses, caps, drainage systems, habitat areas, and additional redevelopment details. The post-NTCRA OMMP is envisioned to be a single document prepared with EPA, and Ecology, and with stakeholder review and input. The OMMP will include sampling and analysis plans as appendices, as well as a schedule for implementation. Each section of the plan will address each of the principal study areas, groundwater monitoring, and the monitoring and maintenance requirements for storm drainage systems serving the upland portions of the EAA. upland habitat resources. The post-removal monitoring plan will be designed to evaluate the effectiveness of source controls measures put in place. These source controls will include periodic comprehensive review of SPU and Port stormwater data for discharges, acquisition of Marina discharges data for sediment COCs, and monitoring of groundwater to establish baseline conditions and changes to flow and character that may occur after the NTCRA. Elements addressed in the OMMP will include, but not necessarily be limited to, the following: Post-removal site conditions and property uses Utility locations Site controls, institutional controls, and access restrictions Perimeter security fencing and on-site buildings Inspection and maintenance of upland caps and coversareas T-117 EAA inspection, monitoring, and maintenance Groundwater and seep monitoring Stormwater system descriptions, operation, maintenance, and storm solids monitoring Erosion and sediment controls Stormwater systems Documentation and reporting Health and safety and waste management for routine and non-routine maintenance The OMMP will also address procedures for managing underlying site soil that may be encountered at depth during any future during post-NTCRA construction within the upland portions of the T-117 EAA (i.e., after completion of the removal action and restoration work done as part of the NTCRA). These procedures will include making necessary notifications, implementing health and safety measures, using appropriate methods for soil stockpiling, performing analytical testing, and pursuing options for soil reuse or disposal at the offsite waste management facility. Additional discussion of the OMMP elements for each T-117 EAA study area is provided in the following Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 265 subsections. A summary of subjects and activities to be addressed in the OMMP is presented in Table 9-3. Table 9-3. Subjects and activities to be addressed in the T-117 OMMP Subject or Activity Rationale Post Removal Action Conditions and Facilities Site features Document final locations Stormwater drainage and treatment Document final locations systems Informational signage Document locations and address maintenance Utility locations Document final locations Stormwater Ongoing assessment of recontamination potential in the EAA and Stormwater monitoring the RAAs Stormwater system maintenance Preventative measure for recontamination, source control Stormwater treatment system operation Preventative measure for recontamination, source control Groundwater and Geotechnical Information Development of post-removal groundwater Necessary to conduct post- removal action groundwater monitoring monitoring network and tidal study Groundwater monitoring Verify that post- removal groundwater RvALs are being met To determine how the removal action alters groundwater flow, Post- removal tidal study particularly at the south end of the Marina Sediment Removal Area Monitoring Sediment area reconnaissance Performance monitoring of sediment backfill/cap areas, if necessary Sediment sampling Assessment of recontamination Requirements for Upland Subsurface Construction To ensure that Port and City control post-removal activities as Notifications prior to construction appropriate within the EAA To ensure that drainage, backfill areas, and erosion control Construction restrictions measures are not compromised Soil handling, disposal, and backfill To ensure safe handling and proper disposal and that final site procedures conditions are properly maintained Site restoration To ensure future construction area(s) are properly restored Upland Area Inspections Performance of erosion control measures (pavements, backfill, planted areas, Source control measure for preventing recontamination. BMPs) Response Actions and Adaptive Management Strategies Groundwater Identify process if post- removal- action groundwater exceed RvALs. Identify process if post- removal- action stormwater solids exceed Stormwater sediment RvALs. Identify process if post- removal- action soil becomes Upland areas recontaminated and exceeds RvALs. Identify process if post- removal- action sediment becomes Sediment area recontaminated and exceeds RvALs. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 266 BMP best management practice EAA early action area OMMP operation, maintenance, and monitoring plan RvAL removal action level 9.54.1 T-117 Sediment Study Area Long-term monitoring of sediment removal areas will include both physical and chemical monitoring to assess site integrity and potential recontamination. Although the intent of the selected alternative is to not rely on capping, if any limited areas are capped (e.g., immediately around in-water structures where dredging might not be feasible), then physical monitoring would be conducted in those areas to evaluate the physical stability of the cap. This would include measurements to evaluate cap thickness and sediment particle size and bathymetric measurements to evaluate evidence of scour from vessel movement or from high-flow events. The Port intends to monitor sediment quality within the T-117 Sediment Study Area, particularly near outfall and seep locations, to determine if recontamination is occurring. Chemical testing will be used following the NTCRA to evaluate ensure that RAOs RvALs, ARARs, and removal objectives are being met, the NTCRA is protective of human health and the environment, and source control continues to be assessedcontinue to be met and assess source control progress with respect to potential recontamination. 9.54.2 T-117 Upland Study Area Post-NTCRA operation, maintenance, and monitoring activities for the T-117 Upland Study Area will depend to a large degree on the final site use of this area. Special controls and mMaintenance procedures and periodic monitoring will be required to maintain ensure that and protect any future habitat resources as that may be established meet their respective performance criteria. If the site is redeveloped for tenant use, then measures will be needed to make sure tenant activities do not compromise the performance of the NTCRA or pose a threat of recontamination to the T-117 Sediment Study Area. The TCRA work plan that was completed for the T-117 Upland Study Area in 2006 (RETEC 2006) provides a good model for post-removal O&M activities, including the monitoring and maintenance of stormwater conveyances and erosion and stormwater controls, inspection and repair of paved areas, and procedures for documenting O&M activities. In addition to these elements, the OMMP will also include prescribed adaptive management procedures to be followed in the event that inspection and monitoring activities detect potential soil erosion and/or recontamination of the T-117 Sediment Study Area originating from the T-117 Upland Study Area. Long-term O&M The OMMP will also include a description of necessary will also discuss (if necessary) procedures for any future post-site development or construction work. These will include notifications prior to construction to ensure that the Port and Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 267 City are made aware of work plans and that appropriate measures are in place to preserve site drainage controls, backfill, and other key structures. Procedures for proper site restoration will also be specified and followed. penetration of the capped areas or excavation at depths that might encounter underlying site soils or sediment. These procedures would include health and safety standards, issues associated with soil stockpiling or analytical testing, and soil reuse or disposal options at the disposal facility. In accordance with the above documents, soil will need to be handled and managed in a manner that is protective of human health and the environment. Site maintenance staff and contractors will be required to follow the relevant OMMP the same procedures as those outlined in the future NTCRA work plan when when performing any post-removal maintenance and construction activities at the T-117 EAA. These procedures will include notification requirements (including contingencies for any activities beyond the planned scope), soil handling procedures, waste management plans and procedures, and required measures for site restoration. Groundwater monitoring will also be required to check for the potential recontamination of the T-117 Upland Study Area and the T-117 Sediment Study Area. Groundwater monitoring points will be located along the future shoreline and Dallas Avenue S.will be located upgradient of the zone of impacted groundwater (i.e., in the vicinity of the boundary between theT-117 Upland Study Area and Dallas Avenue S), with selected wells monitored periodically to confirm stable or decreasing COC concentrations. A full tidal study will be undertaken using monitoring wells within the T-117 upland areas to evaluate the post-removal groundwater regime and how the modified shoreline and site grade has influenced groundwater flow patterns. Monitoring well installation, development, gGroundwater sampling and tidal studies will be completed in accordance with an approved field sampling plan (FSP) and quality assurance project plan (QAPP) to be developed in conjunction with the OMMP. The FSP will include details on sampling methods and frequency, including a long-term monitoring schedule. The QAPP will include project organization, objectives, activities, and quality procedure to be implemented during the compliance monitoring actions. 9.54.3 Adjacent Streets and Residential Yards Study Area As discussed in Section 5.2, since the cessation of asphalt manufacturing facility operations in the mid-1990s, the potential for the recontamination of soils has largely been restricted to the redistribution of existing contaminants. The NTCRA is expected NTCRAs are expected to eliminate the potential for recontamination to T-117 Upland Study Area and Adjacent Streets and Residential Yards Study Area soils from this historical source. 9.54.3.1 Stormwater Stormwater runoff from the Adjacent Streets and Residential Yards Study Area is currently collected in two separate systems that can be roughly divided into areas Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 268 west and east of 17th Avenue S (see Map 2-2). To the west, runoff is currently discharged to the CSS. The cleanup of both of these areas will trigger the stormwater requirements of SMC 22.800 and Directors' Rule 2009-005 (SPU), 17-2009 (DPD) (City of Seattle 2009a). Cleanup west of 17th Avenue S will likely consist of upgrading streets and curbing to current codes, with continued discharge to the CSS. Cleanup options for the area east of 17th Avenue S will include the installation of a permanent stormwater collection/treatment system in accordance with the City and County stormwater codes with discharge to the LDW. The final configuration will be determined in the design phase of the NTCRA and coordinated with the final completion of the T-117 Upland Study Area (e.g., matching drainage and grades with topography of final upland configuration). The method of treating runoff from the adjacent streets will be determined during design. Options include biofiltration swales, filter strips, bioretention cells, wet vaults, and media filtration. The treatment system will be operated and maintained in accordance with SPU protocols. SPU employs standard protocols, which define procedures for inspecting and maintaining the treatment system and associated structures, for each type of system to ensure that these systems remain functional. Stormwater solids monitoring will continue to be performed in accordance with the City's source-tracing program, which is administered by the LDW SCWG. This monitoring will be coordinated with Ecology and EPA to verify that the stormwater solids are not a recontamination concern for LDW sediments. After completion of the NTCRA and implementation of stormwater treatment measures, SPU will monitor the drainage system to evaluate the effectiveness of the removal action and treatment system in controlling PCBs and other contaminants in the runoff from this area. A detailed post-NTCRA monitoring program will be developed during project design;, however, it is anticipated that storm drain monitoring will be conducted by the City and in conjunction with the larger LDW source control program. As currently envisioned, drainage system monitoring will focus on evaluating the chemical characteristics of solids present in this system. Samples of storm solids have proven to be an effective means for identifying pollutant sources and have been used as a benchmark in the assessment of the potential for stormwater solids to recontaminate LDW sediment. Stormwater solids results will be compared with SMS, and threshold concentrations will be identified, which, if exceeded, will trigger additional source investigations. Currently, CSL concentrations are used as a benchmark for triggering source tracing. An adaptive management strategy that will phase in increasingly more aggressive source investigations until the source(s) of any future contamination is identified and controlled will be developed. The adaptive management plan would specify the following: Continued monitoring of solids as may accumulate in stormwater structures (e.g., traps, catch basins, manholes) for the presence and concentration of COCs. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 269 If concentrations of COCs approach some source control reference levels in storm solids samples, the City will determine the source and any additional controls that may be warranted, in which case, storm solids will continue to be monitored once the new/additional control is in -place. If additional control of COC sources is not feasible, then additional stormwater treatment will be evaluated. 9.54.3.2 Groundwater Section 2.3 discusses groundwater conditions beneath the Residential Sstreets and Adjacent Yyards Study Area. Available data indicate that groundwater beneath Residential Streets and Adjacent Yards Study Area has not been impacted. Based on the depth to groundwater (approximately 12 ft) and generally shallow depth of soil removal prism (anticipated to be no greater than 6 ft bgs), it is anticipated that groundwater will not be impacted by the NTCRA. Nevertheless, a pre- and post- NTCRA groundwater monitoring program is necessary, and a groundwater monitoring program for the Adjacent Streets and Residential Yards Study Area will be implemented. The need for and design of a pre- and post-NTCRA groundwater monitoring is anticipated, and a program for Adjacent Streets and Residential Yards Study Area will be evaluated during the design phase of the NTCRA. 9.5.4 Long-term OMMP summary The post-removal monitoring plan will be designed to evaluate the long-term effectiveness of the NTCRA in the three T-117 EAA study areas, including compliance with RAOs and RvALs, effectiveness of source control and other recontamination prevention efforts. The plan will also include procedures for identifying any recontamination effects on the post-NTCRA site and appropriate responses. This may involve strategic sediment sampling (i.e., sampling focused on potential source discharge areas, such as outfalls and seeps) within the T-117 Sediment Study Area, periodic comprehensive review of SPU stormwater data for discharges, the collection of data from Marina discharges for sediment COCs and monitoring of groundwater to establish a groundwater baseline conditions and changes to flow and characteristics that occur as a result ofbecause of the NTCRA. Lower Duwamish Waterway Superfund Site: Revised EE/CA T-117 Early Action Area DRAFT FINAL January 19June 3, 2010 Page 270 10 References AECOM. 2009a. Lower Duwamish Waterway Superfund Site, Terminal 117 Early Action Area. First quarter 2009 interim groundwater monitoring data results - non-time critical removal action. Prepared for the Port of Seattle and the City of Seattle. AECOM, Seattle, WA. AECOM. 2009b. Lower Duwamish Waterway Superfund Site, Terminal 117 Early Action Area. 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