SR 161 - Unnamed Tributaries to Hylebos Creek - Fish Passage

Project overview

Three culverts that block fish passage on tributaries to Hylebos Creek beneath SR 161 in Milton and Federal Way will be replaced with new structures that restore natural stream conditions. Crews also will make habitat improvements within the streams where the pass beneath the state highway. Construction is scheduled to begin in Summer 2025 and continue into fall/winter 2025.

Timeline

Spring 2021 - Fall/Winter 2025

Project status

Construction

Funding

$21.2 Million

What to expect

Construction will begin along SR 161 in Federal Way and Milton as early as June 2025 for the removal of fish barriers on three tributaries to Hylebos Creek.

People should plan for the following during construction:

Weekday single-lane closures on northbound and southbound SR 161 starting in June 2025.
A nine-day full closure on SR 161 between 28th Avenue South and Military Road South to upgrade two separate culverts. This work is tentatively planned for mid-August 2025.
A weekend-long closure on SR 161 between South 370th Street and 28th Avenue South. This work is tentatively planned for September 2025 after Labor Day Weekend.
Signed detours on local streets to guide vehicles, cyclists and pedestrians around extended closures.
Additional traffic and congestion along detour routes during peak traffic times.
Temporary changes to King Country Metro bus routes.

This map shows the locations of three culverts that carry tributaries under SR 161 to Hylebos Creek near Federal Way, WA.

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A map showing the locations of three culverts that will be replaced under SR 161 to Hylebos Creek near Federal Way and Milton.

History and background

Removing fish barriers can deliver impressive benefits, improving fish access for miles up and downstream.

The SR 161 Unnamed Tributaries to Hylebos Creek fish passage replacement project near Federal Way continues to build on our commitment to removing fish barriers on streams that run under state highways. Replacing the outdated culverts with either bridges or fish-passable structures increases the likelihood of fish migration through Hylebos Creek and its tributaries.

There are three culverts that run under SR 161/Enchanted Parkway South, to the south and east of Wild Waves Theme Park. These culverts carry unnamed tributaries under the highway to feed Hylebos Creek. These three culverts range from 18 to 24 inches in diameter. All of them are considered completely impassable to fish.

New fish passages

Replacing these culverts and rebuilding the streams will provide new habitat for the Coho, resident trout, steelhead, and searun cutthroat that use Hylebos Creek and nearby wetlands. Each culvert has a potential habitat gain ranging from 1,066 to more than 1,300 meters. These improvements and habitat gains will help restore fish runs and increase the population of these species.

This benefits commercial seafood operations, recreational fishers, and provides more food for our declining orca population. In addition, replacing these fish barriers helps us meet our obligation to remove barriers under the 2013 U.S. District Court injunction.

This project has been combined into a single contract with fish passage projects on I-90, SR 202 and SR 203.

Design work began in 2021. Guy F. Atkinson Construction was identified as submitting the Apparent Best Value proposal in fall 2023. Construction began on other phases of this fish barrier removal project in spring 2023. Completion is scheduled for early 2027 across all sites.

Utility work on SR 161 began in late 2024. Major construction is scheduled to begin as early as June 2025 on SR 161 and primarily occur in summer and fall 2025.

Milestone

2021

Design

Spring 2022

Project advertisement

October 2022

Guy F. Atkinson Construction identified as submitting the Apparent Best Value proposal

Summer 2025

Construction tentatively scheduled to begin

Fall/Winter 2025

SR 161 construction scheduled to complete

For efficiency and cost savings, this project has been combined with the SR 202 Skunk Creek and SR 203 Unnamed Tributaries to Snoqualmie River, and the I-90 Sunset Creek fish passage projects. The estimated project cost total for the SR 161 unnamed tributaries to Hylebos Creek location is $21.2 million. The estimated project cost total for the three locations combined is $135 million.

This photo shows the existing 24 inch culvert between 28th Avenue South and Military Road South. — The concrete pipe that carries this tributary to Hylebos Creek under SR 161 is only 24-inches in diameter. Located between 28th Avenue South and Military Road South, it will be replaced with a new fish passage that has an opening of at least 31 feet.

This photo shows the existing 24 inch culvert at the intersection of SR 161 and 28th Avenue South near Federal Way — A 24-inch concrete pipe blocks fish passage on this tributary to Hylebos Creek. A new passage with an opening of at least 14 feet will replace it. This culvert is located under SR 161 at the intersection with 28th Avenue South.

This photo shows the existing 18-inch concrete pipe on SR 161 between South 370th and South 372nd streets — Fish can't get up this stream and through the pipe on this tributary located beneath SR 161 between South 370th and South 372nd Streets. The interior of the new fish passage will be at least 35 feet wide.

SR 161 - Unnamed Tributaries to Hylebos Creek - Fish Passage

Project overview

What to expect

History and background

New fish passages

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