COMMISSION 
AGENDA MEMORANDUM                        Item No.          8b 
ACTION ITEM                            Date of Meeting      October 26, 2021 

DATE:     October 15, 2021 
TO:        Stephen P. Metruck, Executive Director 
FROM:    Eileen Francisco, Interim Director, Aviation Facilities and Capital Programs 
Wayne Grotheer, Director, Aviation Project Management 
SUBJECT:  Snow Storage Expansion Project Design Authorization (CIP 801171) 
Amount of this request:               $2,500,000 
Total estimated project cost:         $17,500,000 
ACTION REQUESTED 
Request Commission authorization to design and prepare construction documents for the Snow
Storage Expansion Project (CIP 801171) at Seattle-Tacoma International Airport. The total
request for this action will be $2,500,000 for a total project authorization of $2,794,000. The
estimated overall cost of the project is $17,500,000. 
EXECUTIVE SUMMARY 
The Seattle-Tacoma International Airport (Airport) has historically stored snow in two small,
designated areas at the north and south ends of the airfield, as well as in aircraft cargo and offgate
parking areas. These cargo and parking areas are now occupied with aircraft year-round and
the remaining designated snow storage areas are inadequate for the volume of snow the airport
receives. The project will expand the designated areas available for snow storage and provide
regulatory compliant capture of melt water during typical winter snow events. Melt water from
the snow contains deicing fluids that must be treated. The project will meet the regulatory need
for connection of snow storage areas to the Industrial Waste System (IWS). 
JUSTIFICATION 
Snow storage and melt water disposal capacity is not adequate in the current locations, which
drain to the IWS. When significant snow events occur, snow needs to be temporarily staged in
areas that drain to the storm drainage system or will need to displace aircraft parking positions
within the IWS basin. When untreated melt water discharges outside of the IWS drainage area it
has the potential to negatively impact water quality in adjacent creeks and does not comply with
the Airport's National Pollutant Discharge Elimination Systems (NPDES) permit. Aviation

Template revised January 10, 2019.

COMMISSION AGENDA  Action Item No. __8b__                              Page 2 of 6 
Meeting Date: October 26, 2021 
Environmental has been in discussions with Washington Department of Ecology for a solution for
several years. This project provides that solution. 
When snow is staged outside the designated storage areas, that snow needs to be moved again
from the temporary storage areas (e.g. aircraft parking areas) to the designated storage areas. 
The proposed improvements would allow a larger volume of snow to be placed directly in the
designated storage areas without the need for temporary staging. Therefore, the operational
costs of rehandling snow will decrease. The project will also address safety concerns related to
large dump trucks hauling snow on the vehicle service road (VSR) and operating within the
existing snow storage areas. 
This project meets a regulatory requirement and supports the Century Agenda Goal 4: Be the
greenest and most energy efficient port in North America. Work will be packaged with other
concurrent airfield capital projects to minimize multiple operational impacts and to enhance
safety risk management on the airfield. 
Diversity in Contracting 
The project will be designed using an existing consultant contract with a Women / Minority
Business Enterprise (WMBE) goal of 15%. Project staff is also working with the Diversity in
Contracting Department to develop WMBE aspirational goals for the project's construction
phase. 
DETAILS 
The project includes expansion of the two existing snow storage areas (North and South) as well
as construction of a new snow storage area northeast of Lagoon 3. The north snow storage area
will be expanded by increasing the pavement to the north and improved by lift station capacity
and equipment updates. The existing south snow storage area will be expanded by increasing the
height of the retaining wall and improved through the addition of pavement for truck turning
movements. The proposed SAMP Taxiway A/B project will displace the south snow storage area
if approved. The new Lagoon 3 area will require impacts to wetlands and includes additional
design, permitting, mitigation, and construction requirements for that element. Based on
preliminary information, the Lagoon 3 area site will directly impact approximately 1.8 acres of
wetlands and approximately 2.2 acres of wetland buffers. Design analysis will include employing
an environmental consultant to delineate the quality and quantity of wetlands impacted, as well
as several options for mitigation following standard Washington Department of Ecology protocol. 
Design authorization for the project will support the environmental process and development of
a wetland mitigation plan. The timeline for the additional permitting and wetland mitigation adds
approximately 12 months to the construction schedule for the new Lagoon 3 area improvements. 
For this reason, the project will be phased for design and construction. Phase 1 improvements
will include the work that does not impact wetlands and will be constructed in 2023. Phase 2
work will include work that impacts wetlands. This Phase 2 work, including wetlands mitigation

Template revised June 27, 2019 (Diversity in Contracting).

COMMISSION AGENDA  Action Item No. __8b__                              Page 3 of 6 
Meeting Date: October 26, 2021 
will occur in 2024. The Scope of Work section below includes a list of the project elements
included in each phase. 
The snow storage capacity with this project will allow snow from a 12-inch snowstorm to be
stored with 20% reserve capacity. In contrast, the snow storage capacity at the two existing
facilities can store the snow from approximately a 3-inch snowstorm. The volume of snow to be
stored was developed in consideration of historic snow event records from airport operations
and maintenance and assumptions in the Utility Master Plan. 
Scope of Work 
The project consists of four elements that will be constructed in two phases: 
Phase 1: 
(1)   Expand Existing North Snow Storage Area including IWS Infrastructure Improvements. 
(2)   Expand Existing South Snow Storage Area including additional pavement for vehicle
maneuvering. 
(3)   Widen VSR for Snow Operations Traffic travelling to/from the new area. 
Phase 2: 
(1)   Construct New Snow Storage Area Northeast of Lagoon 3 consisting of new asphalt
storage pad and IWS infrastructure. Wetland mitigation is required for this new storage
area. 
Schedule 
Phase 1 work will be constructed in the 2023 construction season. Phase 2 work will be
constructed in the 2024 construction season. 
Activity 
Design start                                   2021 Quarter 4 
Phase 1 Commission construction          2023 Quarter 1 
authorization 
Phase 1 Construction start                   2023 Quarter 2 
Phase 1 In-use date                          2023 Quarter 4 
Phase 2 Commission construction          2024 Quarter 1 
authorization 
Phase 2 Construction start                   2024 Quarter 2 
Phase 2 In-use date                          2024 Quarter 4 
Cost Breakdown                                     This Request           Total Project 
Design                                                  $2,500,000              2,794,000 
Construction                                                     $0            $14,706,000 
Total                                                         $2,500,000             $17,500,000 

Template revised June 27, 2019 (Diversity in Contracting).

COMMISSION AGENDA  Action Item No. __8b__                              Page 4 of 6 
Meeting Date: October 26, 2021 

ALTERNATIVES AND IMPLICATIONS CONSIDERED 
Alternative 1  Continue existing operational protocol to move snow to various airfield locations
when designated snow storage capacity is exceeded. 
Cost Implications: $0 Capital Investment 
Pros: 
(1)   No initial capital investment. 
Cons: 
(1)   Continued operational expenses due to rehandling snow stored outside of IWS basin.
For example, snow rehandling costs were approximately $360,000 for the three-day
snow-storm in February 2021. 
(2)   Continuing concern for NPDES permit noncompliance when snow is stored outside of
IWS basin 
(3)   Existing infrastructure will need to be replaced in the 1-5 year horizon 
(4)   Regulatory compliant snow storage within IWS basins will need to displace aircraft 
positions 
This is not the recommended alternative. 
Alternative  2    Expand  existing  north  snow  storage  area  including  IWS  infrastructure
improvements. Expand existing south snow storage area including additional pavement for
vehicle maneuvering. 
Cost Implications: $6,000,000 
Pros: 
(1)   Increases snow storage capacity in existing familiar areas 
Cons: 
(1)   Potential operational expense due to rehandling of snow stored outside of IWS basin 
(2)   Continuing concern for NPDES permit noncompliance when snow is stored outside of
IWS basin 
(3)   Does not meet full snow storage needs  regulatory compliant snow storage will need
to displace aircraft parking positions 
(4)   Construction will have temporary operational impacts 
This is not the recommended alternative. 
Alternative 3    Expand Existing North Snow Storage Area including IWS Infrastructure
Improvements. Expand Existing South Snow Storage Area including additional pavement for
vehicle maneuvering. Construct New Snow Storage Area Northeast of Lagoon 3 consisting of new


Template revised June 27, 2019 (Diversity in Contracting).

COMMISSION AGENDA  Action Item No. __8b__                              Page 5 of 6 
Meeting Date: October 26, 2021 
asphalt storage pad and IWS infrastructure. Widen VSR for Snow Operations Traffic travelling
to/from the new area. 
Cost Implications: $17,500,000 
Pros: 
(1)   Snow storage capacity will be increased to meet need based on historical snow events 
(2)   Snow storage meltwater will flow to the IWS, meeting regulatory requirements 
(3)   Annual operating costs for snow handling will be reduced 
Cons: 
(1)   Requires capital expenditure now 
(2)   Construction will have temporary operational impacts 
This is the recommended alternative. 
FINANCIAL IMPLICATIONS 
Cost Estimate/Authorization Summary              Capital        Expense           Total 
COST ESTIMATE 
Original estimate                                 $8,177,000               $0      $8,177,000 
Current change                                $9,323,000               0      $9,323,000 
Revised estimate                              $17,500,000               0      17,500,000 
AUTHORIZATION 
Previous authorizations                            $294,000                0        $294,000 
Current request for authorization                $2,500,000                0      $2,500,000 
Total authorizations, including this request       $2,794,000                0      $2,794,000 
Remaining amount to be authorized            $14,706,000              $0    $14,706,000 
Annual Budget Status and Source of Funds 
This project, CIP C801171, was included in the 2021-2025 capital budget and plan of finance with
a budget of $8,177,000. A budget increase of $9,323,000 was transferred from the Aeronautical
Reserve CIP (C800753) resulting in zero net change to the Aviation capital budget. The funding
source would be Airport Development Fund and revenue bonds. The Majority in Interest proposal 
was submitted to the airlines for review.
Financial Analysis and Summary 
Project cost for analysis              $17,500,000 
Business Unit (BU)                  Airfield Movement Area 
Effect on business performance     NOI after depreciation will increase due to inclusion of
(NOI after depreciation)             capital (and operating) costs in airline rate base 
IRR/NPV (if relevant)                N/A 
CPE Impact                       $.03 in 2023 and $.05 in 2025 

Template revised June 27, 2019 (Diversity in Contracting).

COMMISSION AGENDA  Action Item No. __8b__                              Page 6 of 6 
Meeting Date: October 26, 2021 

ATTACHMENTS TO THIS REQUEST 
(1)   Presentation slides 
PREVIOUS COMMISSION ACTIONS OR BRIEFINGS 
None 
















Template revised June 27, 2019 (Diversity in Contracting).