Hoot, hoot. Night owls, take note: Nightly closures of South 200th Street in SeaTac begin next week, from Tuesday, Feb. 3 through the morning of Friday, Feb. 6, the Washington State Department of Transportation (WSDOT) announced.

The closures will allow crews to build bridge foundations for the SR 509 Expressway’s flagship bridge.

When completed, the bridge will be 1,587 feet long and cross over the Des Moines Creek wetland, South 200th Street and the Lake to Sound Trail.

Additionally, lane and ramp closures on SR 509 in SeaTac and Burien continue Monday, Feb. 2 through the morning of Tuesday, Feb. 3.

Lane and ramp closures on SR 509 will allow crews to replace guardrails and landscape.

This work is part of the SR 509 Completion Project.

South 200th Street closure information

Tuesday, Feb. 3 through the morning of Friday, Feb. 6:

  • 9 p.m. to 4 a.m. – South 200th Street will close nightly in both directions between 18th Avenue South and Des Moines Creek Trail. A signed detour will be in place.

SR 509 lane closure information

Monday, Feb. 2 through the morning of Tuesday, Feb. 3:

  • 8 p.m. to 5 a.m. – One lane in each direction of SR 509 will close overnight between South 176th and South 188th streets.

SR 509 ramp closure information

Monday, Feb. 2 through the morning of Tuesday, Feb. 3:

  • 7 p.m. to 5 a.m. – The Des Moines Memorial Drive South on-ramp to northbound SR 509 will close overnight. A signed detour will be in place.
  • 10 p.m. to 5 a.m. – The South 160th Street on-ramp to southbound SR 509 will close overnight. A signed detour will be in place.

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, 2025 and a new tunnel under I-5 at the SR 516 interchange opened on July 16, 2025. 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.

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.