Project overview
Three culverts block fish passage on tributaries to Hylebos Creek that flow beneath SR 161 in Federal Way and Milton. These three culverts are located along the state highway between South 370th Street and Military Road South. Construction will begin in 2025 to prepare for culvert replacement, which will happen during the summer 2026 construction season.
The new culverts will allow fish to swim upstream more easily while helping to restore natural stream conditions beneath SR 161. The project also will improve habitat within the waterways where they flow beneath the state highway.
What to expect
Construction will begin along SR 161 in Federal Way and Milton as early as June 2025. People should plan for the following during the 2025 construction season:
- Continuous right lane closures on both directions of SR 161 near South 370th Street from late July through September.
- Continuous single-lane closure of South 370th Street near the SR 161 intersection for sewer work. A signed detour is in place.
Upgrading two culverts on SR 161 between 28th Avenue South and Military Road South will require a 24-hour-a-day full closure on all lanes of SR 161 lasting roughly nine days.
Upgrading the culvert near South 370th Street will require a 24-hour-a-day full closure on all lanes of SR 161 for roughly three days over a single weekend.
Signed detours will be in place during SR 161 closures for culvert removal.
These closures will occur during the summer 2026 construction season.
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 Replacing the outdated culverts with either bridges or fish-passable structures increases the likelihood of fish migration through Hylebos Creek and its tributaries.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.
