Roundabout construction at the South 160th Street and SR 509 interchange in Burien is picking up speed, ushering in three consecutive weekend-long closures, the Washington State Department of Transportation (WSDOT) announced.
Beginning this Friday, Aug. 8, 2025, crews will close South 160th Street between 5th Place South and Ambaum Cut Off South, and nearby SR 509 ramps round-the-clock for three weekends:
- Friday, Aug. 8 – Monday, Aug. 11
- Friday, Aug. 15 – Monday, Aug. 18
- Friday, Aug. 22 – Monday, Aug. 25
These weekend-long closures will allow crews to continue building two new roundabouts at the South 160th Street and SR 509 interchange.
This work is part of the SR 509 Completion Project.
South 160th Street closure information
Friday, Aug. 8 through the morning of Monday, Aug. 11:
- 8 p.m. to 5 a.m.: South 160th Street will close in both directions between Ambaum Cut Off South and 5th Place South.
SR 509 ramp closure information
Friday, Aug. 8 through the morning of Monday, Aug. 11:
- 9 p.m. to 5 a.m.: The South 160th Street on-ramp to northbound SR 509 will close.
- 9 p.m. to 5 a.m.: The South 160th Street on-ramp to southbound SR 509 will close.
- 10 p.m. to 5 a.m.: The northbound SR 509 exit to South 160th Street will close.
South 160th Street and SR 509 ramp detour information
Drivers on South 160th Street will detour to South 156th Street or South 168th Street. Local access to 5th Place South, all residential driveways and business access will be maintained. Sidewalk users and bicyclists will follow a detour on the south side of South 160th Street.
There will be no access to SR 509 from South 160th Street. The northbound SR 509 off-ramp will also be closed. Signed detours will be in place for all ramp closures. Detour routes will include First Avenue South, Des Moines Memorial Drive South, South 188th and South 148th streets. The southbound SR 509 off-ramp to westbound South 160th Street will remain open.
SR 509 Completion Project information
The SR 509 Completion Project builds 3 miles of new tolled highway between I-5 and South 188th Street near the south end of Seattle-Tacoma International Airport. The new highway will be completed in stages. The portion between I-5 and 24th Avenue South opened on June 28 and a new tunnel under I-5 at the SR 516 interchange opened on July 16. The final stage builds the remaining 2 miles of the expressway between 24th Avenue South and South 188th Street. The entire project is planned for completion by 2029.
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Puget Sound Gateway Program overview
The SR 509 Completion Project is part of WSDOT’s Puget Sound Gateway Program, which also includes the SR 167 Completion Project in Pierce County. Together, the two completion projects finish critical missing links in Washington’s highway and freight network.
