Template revised January 10, 2019.
COMMISSION
AGENDA MEMORANDUM
Item No.
8k
ACTION ITEM
Date of Meeting
August 11, 2026
DATE: July 30, 2026
TO: Stephen P. Metruck, Executive Director
FROM: Eileen Francisco, Director, Aviation Project Management
Sarah Cox, Director, Aviation Environment & Sustainability
SUBJECT: Industrial Wastewater Treatment Plant (IWTP) Enhancements – CIP# C801234
100% Design Funding and Early Works Package Release
Amount of this request:
$ 41,200,000
Total estimated project cost:
$ 280,782,000
ACTION REQUESTED
Request Commission authorization for the Executive Director to (1) authorize full design and
preparation of construction documents for the Industrial Wastewater Treatment Plant
Enhancements projects; (2) procure long-lead items; (3) authorize Port Construction Services to
execute small works contracts and use Port crews for support of construction; (4) execute early
work packages with Hoffman Construction; (5) increase project authorization by $41,200,000 for
a total project authorization of $61,335,000. The total estimated Industrial Wastewater
Treatment Plan Enhancements project cost is $280,782,000.
EXECUTIVE SUMMARY
This project will install a pre-treatment system and upgrade the existing systems at the IWTP to
ensure compliance with future King County Department of Natural Resources Industrial Waste
Discharge permit limits.
The airport’s IWTP manages and treats stormwater associated with industrial activities from
aircraft fueling and maintenance operations as well as wastewater from other airport related
operations such as aircraft deicing. Stormwater runoff with low Biochemical Oxygen Demand
(BOD) discharges to the Puget Sound under conditions of National Pollutant Discharge
Elimination Systems (NPDES) permit. Stormwater runoff with high BOD discharges to King County
South Treatment Plant for secondary treatment under King County Department of Natural
Resources Permit No. 7810-06. The primary source of high BOD is aircraft deicer runoff. Effective
in 2026, the King County BOD permit limits will be restricted to a level that will require an on-site
pre-treatment system at the Seattle–Tacoma International Airport (SEA). Negotiations with King
COMMISSION AGENDA – Action Item No. 8k Page 2 of 7
Meeting Date: August 11, 2026
Template revised June 27, 2019 (Diversity in Contracting).
County regarding the implementation schedule require the Port to demonstrate progress
towards the implementation measures necessary to meet the new permit limits.
The amount of this request is $41,200,000 to complete the full Architecture and Engineering
(A&E) design of the IWTP Program (CIP C801234), long-lead equipment purchases, and
completing early works packages. The total estimated project cost is currently $ 280,782,000.
Staff will return to the Commission following the completion of the 90% design and negotiation
for the Maximum Allowable Construction Cost (MACC), at that time staff will provide an updated
project cost estimate and request authorization to move forward with the full construction
package.
JUSTIFICATION
Since 2007, the IWTP has discharged industrial wastewater runoff containing aircraft deicers to
the King County Wastewater Treatment System. Through each permit cycle, King County has
restricted discharges because under sustained heavy aircraft deicer loads, the performance of
the County’s treatment plant has been disrupted by the Port’s discharges.
Over the past five years, the Port has evaluated technologies and methods to reduce impacts to
the King County treatment plant. This evaluation included a comprehensive assessment of
deicing source control, storage, and treatment technologies. This assessment resulted in
measures to reduce the amount of aircraft deicer applied and implemented operational
efficiencies. For example, most of the aircraft deicer applicators switched to an application
technology reducing the amount of deicer applied. This source reduction reduces the amount of
future storage needed.
Under the terms of the July 2021 and July 2026 Industrial Waste Discharge (IWD) permits, the
Port is required to implement infrastructure and operational modifications by 2031 to comply
with future discharge limits. The previous BOD mass loading limit of 60,000 lb./day will be
reduced to 15,000 lb./day maximum daily and 12,000 lb./day on a monthly average basis during
the 2031 permit issuance, with interim limits imposed in the 2026 permit cycle. The IWTP
modifications needed to comply with these reduced limits include significant additions to the
system for storage and pretreatment of IWS stormwater containing spent aircraft deicing fluid.
The 2026 IWD permit also includes a compliance schedule over the next five years to reflect
progress toward implementation of measures to meet further reduced 2031 effluent limitations.
The Port will continue to collaborate with King County Industrial Waste Program to meet permit
limits during construction of the project.
While the Port has developed a preliminary design of the pretreatment and storage systems,
some elements of the design scope present risks to overall cost and schedule (phasing, controls
architecture, storage requirements, seasonal modeling, etc.).
Diversity in Contracting
There will be a 15% WMBE aspirational goal associated with this contract from the designers.
The construction determination will be made at the 60% set.
COMMISSION AGENDA – Action Item No. 8k Page 3 of 7
Meeting Date: August 11, 2026
Template revised June 27, 2019 (Diversity in Contracting).
DETAILS
Funds will be used to develop and complete:
• Complete Design (treatment configuration, storage options, infrastructure needs)
• Final construction estimate
• Determine all jurisdictional and utility districts design input
o PSE Power requirements
o Highline Water District
o Midway Sewer District
o City of SeaTac requirements
The completed design will provide clarity of a pre-treatment system, water storage, and all
associated mechanical support systems that will work with the existing systems.
Scope of Work
Design completion of the following systems will be included in the scope of the IWTP Program
(1) Existing IWTP upgrades (lagoon mixing, modifications to Dissolved Air Flotation systems
(DAF’s), etc.)
(2) Pre-treatment flow diversion and influent system
(3) Storage systems to facilitate pre-treatment
(4) BOD treatment system (aerated gravel beds, oil-water separator, drainage, etc.)
(5) Effluent discharge systems
(6) Support systems (new building, power supply, controls, security systems, HVAC)
(7) Early Works Package to include the procurement/construction:
a. Long Lead Equipment purchase.
b. Medium Intensity Approach Lighting System with Runway Alignment Indicator
Lights (MALSR) work
c. PSE demolition and new work
(8) Convert Parking garage drainage from Industrial Waste System (IWS) to Storm Drainage
Schedule
Activity
60% Design Complete
90% Design Complete
100% Design Complete
Maximum Allowable Construction Cost
(MACC) Determined
Commission Authorization – Construction
Notice to Proceed
Substantial Completion
COMMISSION AGENDA – Action Item No. 8k Page 4 of 7
Meeting Date: August 11, 2026
Template revised June 27, 2019 (Diversity in Contracting).
Cost Breakdown
This Request
Total Project
Design
$13,225,000
$54,906,000
Construction
$27,975,000
$225,886,000
Total
$41,200,000
$ 280,792,000
ALTERNATIVES AND IMPLICATIONS CONSIDERED
Alternative 1 – Status Quo. Project will need to expense $15,000,000
Cost Implications: $15,000,000
Pros:
(1) No further expenditure of capital.
Cons:
(1) BOD levels would exceed permit allowances and likely result in significant fines
indefinitely
(2) Failure to meet King County permit levels for the new permit cycle will leave limited
options for managing de-icing runoff at STIA. High BOD wastewater at the IWTP will not
be able to discharge to the King County South Treatment Plant
(3) The IWTP current storage is not sufficient and could result in overflow of untreated
water into adjacent receiving waters
(4) High risk of violating King County and/or Department of Ecology NPDES permit
requirements
(5) Increased risk of King County restricting or ceasing discharges during high-risk
operational periods.
(6) Staff have evaluated other treatment options locally and regionally outside of
discharging to King County and did not identify feasible options
(7) Without the project, winter flight operations would need to be restricted (i.e., flight
cancellations) to maintain compliance
Alternative 2 – Construct new IWTP Facility with full scope
Cost Implications: $ 310,631,000
Pros:
(1) Maintain SEA Operations
(2) Comply with King County and Department of Ecology (NPDES) permit requirements
(3) Implementation of a pre-treatment facility on-site at STIA will allow continued discharge
to the King County South Treatment Plant.
(4) No need for future DAF project
COMMISSION AGENDA – Action Item No. 8k Page 5 of 7
Meeting Date: August 11, 2026
Template revised June 27, 2019 (Diversity in Contracting).
(5) Improved operational flexibility
Cons:
(1) Highest Cost
This is not the recommended alternative
Alternative 3 – Construct new IWTP Facility with deferred scope.
Cost Implications: $280,792,000
Pros:
(1) Maintain SEA Operations
(2) Comply with King County and Department of Ecology (NPDES) permit requirements
(3) Implementation of a pre-treatment facility on-site at STIA will allow continued discharge
to the King County South Treatment Plant.
Cons:
(1) Dissolved Air Flotation (DAF) tanks need to be replaced in five years
(2) Reduced operational flexibility at lagoon 3
This is the recommended alternative.
FINANCIAL IMPLICATIONS
Cost Estimate/Authorization Summary
Capital
Expense
Total
COST ESTIMATE
Original estimate
$ 127,000,000
$0
$ 127,000,000
Transfer from IWTP Controls
$ 10,600,000
$ 10,600,000
Transfer from Aeronautical Reserve
$49,400,000
$49,400,000
Previous Budget Estimate Range
$200,000,000
to
$300,000,000
0
$200,000,000
to
$300,000,000
Current Budget Change
• From $200,000,000
$93,782,000
0
$93,782,000
Revised estimate
$ 280,782,000
0
$ 280,782,000
AUTHORIZATION
Previous authorizations
$ 20,135,000
0
$ 20,135,000
Current request for authorization
$ 41,200,000
0
$ 41,200,000
Total authorizations, including this request
$ 61,335,000
0
$ 61,335,000
Remaining amount to be authorized
$ 219,447,000
$0
$ 219,447,000
COMMISSION AGENDA – Action Item No. 8k Page 6 of 7
Meeting Date: August 11, 2026
Template revised June 27, 2019 (Diversity in Contracting).
Annual Budget Status and Source of Funds
This project, CIP C801234, was included in the 2026-2030 capital budget and plan of finance with
a budget of $187,000,000. The budget increase of $93,782,000 was transferred from the
Aeronautical Allowance to CIP C800753 resulting in no net change to the Airport capital budget.
The funding sources would include the Airport Development Fund and revenue bonds. Most of
the project costs would be recovered through airlines rates.
Financial Analysis and Summary
Project cost for analysis
$280,782,000
Business Unit (BU)
Airfield Apron Area
Effect on business performance
(NOI after depreciation)
NOI after depreciation will increase due to inclusion of
capital (and operating) costs in airline rate base.
IRR/NPV (if relevant)
N/A
CPE Impact
$0.70 in 2030
Future Revenues and Expenses (Total cost of ownership)
Aviation Operations and Maintenance have reviewed the preliminary design of the system, and
meetings have been held with leadership from each group to discuss expected additional costs
of ownership. The preliminary design documentation includes a summary of expected additional
operators needed to support the system, as well as additional maintenance and spare part
requirements.
ATTACHMENTS TO THIS REQUEST
(1) Presentation slides
PREVIOUS COMMISSION ACTIONS OR BRIEFINGS
July 23, 2024 – The Commission authorized the Executive Director to (1) advertise and
execute a General Contractor, Construction Manager (GC/CM) construction contract and
authorize pre-construction services for CIP# C801234. The amount requested under this
authorization was $6,500,000.
September 26, 2023 (item 8b) – The Commission authorized the Executive Director to (1)
advertise and execute a project specific contract for Architecture and Engineering (A&E)
services, (2) develop a project notebook document and progress the overall design to
30%, (3) utilize port crews for enabling work related to the Industrial Wastewater
Treatment Plant (IWTP) project at Seattle-Tacoma International Airport. The amount
being requested under this authorization was $11,500,000.
COMMISSION AGENDA – Action Item No. 8k Page 7 of 7
Meeting Date: August 11, 2026
Template revised June 27, 2019 (Diversity in Contracting).
December 14, 2021 – The Commission authorized execution of a contract for Architecture
and Engineering (A&E) services to complete planning and preliminary design for the
Industrial Wastewater Treatment Plant (IWTP) Program (CIP C801234). The amount of
this request was $2,000,000.