Template revised January 10, 2019.
COMMISSION
AGENDA MEMORANDUM
Item No.
8j
ACTION ITEM
Date of Meeting
April 26, 2022
DATE: April 15, 2022
TO: Stephen P. Metruck, Executive Director
FROM: Eileen Francisco, Interim Director, AV Facilities & Capital Programs
Wayne Grotheer, Director, Aviation Project Management Group
SUBJECT: Tyee Pond Effluent Pipe Replacement (C801173)
Amount of this request:
$390,000
Total estimated project cost:
$2,540,000
ACTION REQUESTED
Request Commission authorization for the Executive Director to complete design for the Tyee
Pond Effluent Pipe Replacement Project located just south of the Seattle-Tacoma International
Airport in the amount of $390,000. The total estimated project cost is $2,540,000.
EXECUTIVE SUMMARY
The Tyee Pond stormwater pond and its control structures are a regional detention facility that
the Port of Seattle owns, maintains, and operates. This detention facility is regulated by the
Department of Ecology (DOE) Dam Safety Program. The downstream effluent pipe is over 30
years old and shows signs of damage and deterioration. The pipe needs to be replaced to ensure
that the detention facility and downstream effluent pipe can function as designed for the next
50 years. Emergency repairs have already been needed and DOE issued a requirement for a
permanent repair to be completed by 2025.
JUSTIFICATION
This project will support the following Century Agenda goals:
• To be the greenest and most energy-efficient port in North America by meeting or
exceeding agency requirements for stormwater leaving Port-owned or operated
facilities.
• To become a model for equity, diversity, and inclusion by increasing utilization of
Women and Minority Business Enterprise (WMBE) and Disadvantage Business
Enterprise (DBE) firms and eliminating disparity of access to opportunities.
In December 2021, a pipe assessment was completed that examined the existing pipe
downstream of the repaired section (approximately 382 linear feet). The Pipe Assessment Report
noted joint separation, deformation, and corrosion in the downstream pipe and recommended
COMMISSION AGENDA – Action Item No. _8j_ Page 2 of 4
Meeting Date: April 26, 2022
Template revised June 27, 2019 (Diversity in Contracting).
replacing the entire pipe. If the pipe completely fails, the hydraulics of Des Moines Creek will be
affected impacting the downstream salmon bearing creek habitat. In the worst-case scenario,
with the detention facility at full capacity, the pipe failure can result in the failure of the Tyee
Pond embankment sending several thousand gallons of stormwater towards downstream
residents adjacent to Des Moines Creek in an uncontrolled fashion.
Diversity in Contracting
The design of this project will utilize an existing indefinite delivery indefinite quantity (IDIQ)
contract that has an established WMBE goal of 10%. The project team will work with Diversity in
Contracting department to establish additional WMBE goals within the construction phase of this
effort.
DETAILS
Tyee Pond is located south of Seattle-Tacoma International Airport and is located on the east fork
of Des Moines Creek flowing south from Bow Lake. The pond has a capacity of 19.7 acre-ft and is
therefore regulated by DOE Dam Safety program. The pond and effluent pipe were originally
constructed in the late 1980’s. In 2020, emergency repairs were made to a small section of the
pipe (approximately 32 linear feet) that was leaking and causing sinkholes to appear on the pond
embankment above the pipe. DOE accepted the interim repairs but required a permanent repair
by 2025.
Scope of Work
The project will replace the entire downstream effluent pipe with a 72-inch diameter reinforced
concrete pipe. In addition, two manhole structures will be added to the northern section of the
pipe to provide energy dissipation.
Schedule
Commission design authorization
2022 Quarter 2
Design start
2022 Quarter 2
Commission construction authorization
2023 Quarter 1
Construction start
2023 Quarter 2
In-use date
2023 Quarter 4
Cost Breakdown
This Request
Total Project
Design
$390,000
$625,000
Construction
$0
$1,915,000
Total
$390,000
$2,540,000
COMMISSION AGENDA – Action Item No. _8j_ Page 3 of 4
Meeting Date: April 26, 2022
Template revised June 27, 2019 (Diversity in Contracting).
ALTERNATIVES AND IMPLICATIONS CONSIDERED
Alternative 1 – No improvements
Cost Implications: $0
Pros:
(1) Requires no capital investment
Cons:
(1) Does not address integrity of Tyee Pond dam required by DOE
(2) Does not address long-term viability of the storm water infrastructure
This is not the recommended alternative.
Alternative 2 – Utilize the bypass system
Cost Implications: $702,000
Pros:
(1) Requires less capital investment
Cons:
(1) Does not address integrity of Tyee Pond dam required by DOE
(2) Does not address long-term viability of the storm water infrastructure
(3) Potential to damage downstream salmon bearing creek habitat (and trigger fines)
This is not the recommended alternative.
Alternative 3 – Replace the effluent pipe
Cost Implications: $2,540,000
Pros:
(1) Permanent solution ensuring Tyee Pond dam integrity
(2) Offers maximum stormwater flow control from the Tyee Pond
(3) Doesn’t adversely impact flow to downstream salmon bearing creek
Cons:
(1) Requires greater capital investment
(2) Permits may be required by the Corps of Engineers to complete this project potentially
delaying project completion by a year.
This is the recommended alternative.
COMMISSION AGENDA – Action Item No. _8j_ Page 4 of 4
Meeting Date: April 26, 2022
Template revised June 27, 2019 (Diversity in Contracting).
FINANCIAL IMPLICATIONS
Cost Estimate/Authorization Summary
Capital
Expense
Total
COST ESTIMATE
Original estimate
$2,791,000
$0
$2,791,000
Current change
($251,000)
$0
($251,000)
Revised estimate
$2,540,000
$0
$2,540,000
AUTHORIZATION
Previous authorizations
$235,000
$0
$235,000
Current request for authorization
$390,000
$0
$390,000
Total authorizations, including this request
$625,000
$0
$625,000
Remaining amount to be authorized
$1,915,000
$0
$1,915,000
Annual Budget Status and Source of Funds
This project CIP #801173 was included in the 2022-2026 capital budget and plan of finance as a
budget of $2,791,000. A budget decrease of $251,000 was transferred to the Aeronautical
Reserve (CIP #800753) resulting in a zero-net change to the Aviation capital budget. The funding
source for this project will be the Airport Development Fund (ADF) and revenue bonds.
Financial Analysis and Summary
Project cost for analysis
$2,540,000
Business Unit (BU)
Airfield Movement 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
$.01 in 2024
Future Revenues and Expenses (Total cost of ownership)
Operations and maintenance costs are anticipated to be minimal. The pipe will be video
inspected once every 3-5 years.
ATTACHMENTS TO THIS REQUEST
(1) Vicinity Map
PREVIOUS COMMISSION ACTIONS OR BRIEFINGS
None
