Drivers should expect an overnight directional closure of the SR 509 Expressway in SeaTac Tuesday, April 14 to the morning of Wednesday, April 15, according to the Washington State Department of Transportation.
This closure will allow WSDOT crews to perform electrical work.
This work is part of the SR 509 Completion Project.
SR 509 Expressway closure information
Tuesday, April 14 to the morning of Wednesday, April 15:
- 10 p.m. to 6 a.m. – The southbound SR 509 expressway will close overnight from 24th Avenue South to I-5. 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.
