Item 7c Supp

Item No.    7c Supp
Date of Meeting November 30, 2009
Port of Seattle
T-5 Maintenance Dredging
Update
Port of Seattle Commission Briefing
November 30, 2009

T-5 Maintenance Dredging

Background:
In September 08 Commission authorized
$680K (expense project) for design and
permitting
Proposal included all berths in one dredging
event to be completed by February 15, 2010


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T-5 Maintenance Dredging
Project
Area




3

T-5 Maintenance Dredging

Recent events:
Current operating budget constraints
Delays and phased construction approach to defer
spending
More time to pursue a long-term strategic
maintenance permit
Met with permit agencies regarding long-term
maintenance permit
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T-5 Maintenance Dredging

Proposed long-term strategy addresses:
Issues such as equipment tolerances
Frequent sloughing/shoaling at T5
Minimum safety for newer deep draft vessels
Future changes to sediment standards- upland vs.
open water disposal
Phasing: Berth 2 in early 2011, Berths 1 & 3 later

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T-5 Maintenance Dredging
Equipment tolerances (previous experience):
Sheltered, harbor conditions
Mechanical dredge
Tight dredging standards (1' OD)
14
Vertical Elevation (Feet)  12
10
8
6
4                                    50% Available Material (0-2 ft)
2
5% Available Material (2-4 ft)
0
20  40  60  80  100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520
Horizontal Cross-Section Distance (Feet)
Pre-Dredge Elevations                  Post-Dredge Elevations                  2 ft below Required Dredge Depth
Required Dredging4 ft below Required Dredge DepthDredging 0  2 ft below Required DepthRequired Dredge Depth          Dredging 2  4 ft below Required Depth


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T-5 Maintenance Dredging

Intent of Overdepth
Reflective of project conditions
Reflective of dredge capabilities
Avoid permit non-compliance for incidental
depth excursions
Not intended to obtain deeper than permitted
project depths

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T-5 Maintenance Dredging
Dredge Prism
Pre-Dredge
Bottom
Project Depth
( -45 MLLW or
Required Dredging
-50 MLLW )
Depth (Project Depth +
1' Advance Maintenance)
Advance
Maintenance
Dredging (1ft)                                           Sediment
Undredged
Material                                           1 ft
Post Dredge          Characterization Depth
2 ft                  Surface
( Z-Layer )
Limited Incidental
Dredging                  Anticipated
<10% Removal              Overdepth
Dredging (2ft)
50%-75%
Removal

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T-5 Maintenance Dredging
Proposed New Strategy
10 Year Programmatic Permit
Phased dredging over 10 years
Streamlines regulatory process
Eliminates perception of 'piecemeal' approach
One foot (1') advance maintenance to extend interval between
events, increase safety, lower cost, lower emissions (EX-15)
Two feet (2') overdepth for equipment tolerances, vessel safety,
compliance & contracting
50-75% sediments removed from 0'- 2' below required depth
Zone of incidental excursions
5-15% sediments removed from 2'- 4' below required depth
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T-5 Maintenance Dredging
Phase I
Dredge 1000' l.f. (Berth 2)
Scheduled 2010/2011 dredging season
Dredging to include 1' advance maintenance and 2' overdepth
Provisions for incidental excursions below overdepth limits
+/- 3,000 cubic yards
Phase I construction costs depend on DMMO determination



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T-5 Maintenance Dredging
Phase II
Berth 1 and Berth 3
Dredging to include 1' advance maintenance and 2' overdepth
Provisions for incidental excursions below overdepth limits
Dredge during 2011/2012 or 2012/2013 dredging season (if
budget permits)
+/- 11,300 cubic yards
Requires new Suitability Determination from DMMO subject to
future standards
Berth 3 requires further study of slope stability (slope stabilization
work is not included in the programmatic permit)

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T-5 Maintenance Dredging
Phase III: Subsequent Maintenance
10-year period
Estimated 1-3 year frequency
Not to exceed 40,000 cubic yards over ten year period
Each event requires notification/coordination:
U.S. Army Corps of Engineers
Dredged Materials Management Office
Muckleshoot & Suquamish Tribes
Environmental Protection Agency
Washington State Dept. of Ecology
Washington State Dept. of Fish & Wildlife
City of Seattle
NOAA Fisheries/US Fish & Wildlife Service
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T-5 Maintenance Dredging
Next steps:
For 2009
1.  Submit JARPA for Programmatic Maintenance Permit
2.  Undertake required agency consultation/coordination
For 2010:
1.  Receive regulatory approvals
2.  Final design, bid, and construct Phase 1/Berth 2
3.  Commission authorization for bid/award/construction
for Phase I (anticipated summer 2010)
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