Weekday right lane closures on northbound and southbound SR 161 begin the week of June 22, 2026, between South 370th Street and Military Road South for preliminary construction.
Project overview
Three tributaries to Hylebos Creek flow beneath SR 161 in Federal Way and Milton through culverts that prevent fish from swimming upstream. These three culverts are located between South 370th Street and Military Road South. During the 2026 construction season, contractor crews will replace these three culverts with new fish-passable structures that restore natural stream conditions beneath SR 161. The project also will improve habitat within the waterways beneath and around the state highways.
What to expect
Preliminary construction began during the 2025 construction season at all three culvert locations. Major construction is planned during the 2026 construction season.
June 2026
Construction resumes the week of June 22. People should plan for about three weeks of right lane closures Monday through Friday from 7 a.m. to 3 p.m. between South 370th Street and Military Way South.
Mid-July 2026
Around-the-clock SR 161 right lane closures begin in mid-July between South 370th Street and Military Way South for construction.
July 24-27 full closure
All lanes of SR 161 will close around the clock between 28th Avenue South and 20th Avenue South/South 360th Street for culvert installation across the highway near South 370th Street. Signed detours will be available throughout the weekend closure.
Continuous right lane closures on both directions of SR 161 resume July 27.
Aug. 7-17 full closure
All lanes of SR 161 will close around the clock between 28th Avenue South and Military Road South for culvert installation on two culverts across the highway near 28th Avenue South. Signed detours will guide people around the closure.
Continuous right lane closures on both directions of SR 161 resume Aug. 17 through much of September.
October 2026
Construction concludes at all three locations (tentative).
A map showing the locations of three culverts that will be replaced under SR 161 to Hylebos Creek near Federal Way and Milton.
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 Replacing the outdated culverts with either bridges or fish-passable structures increases the likelihood of fish migration through Hylebos Creek and its tributaries.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.
