8j. Memo

Tyee Pond Effluent Pipe Replacement Project

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 
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. 
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. 
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
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

Template revised January 10, 2019.

COMMISSION AGENDA  Action Item No. _8j_                                 Page 2 of 4 
Meeting Date: April 26, 2022 
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
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. 
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 

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

COMMISSION AGENDA  Action Item No. _8j_                                 Page 3 of 4 
Meeting Date: April 26, 2022 
Alternative 1  No improvements 
Cost Implications: $0 
(1)   Requires no capital investment 
(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 
(1)   Requires less capital investment 
(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 
(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 
(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. 

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

COMMISSION AGENDA  Action Item No. _8j_                                 Page 4 of 4 
Meeting Date: April 26, 2022 
Cost Estimate/Authorization Summary               Capital        Expense           Total 
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 
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 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                       $.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. 
(1)   Vicinity Map 

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

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