Drivers should plan for overnight lane and ramp closures on SR 509 in SeaTac and Burien and ramp closures on SR 516 in Kent from Thursday, April 23 to the morning of Friday, April 24, according to the Washington State Department of Transportation (WSDOT).

Ramp closures on SR 509 and SR 516 will allow contractor crews working for WSDOT to add new lane lines and road markings that help guide drivers and clearly define lanes.

Lane closures on SR 509 will allow crews to build barriers that help separate traffic and improve safety.

This work is part of the SR 509 Completion Project.

SR 509 lane closure information 

Thursday, April 23 to the morning of Friday, April 24:

  • 8 p.m. to 5 a.m. – One lane in each direction of SR 509 will close overnight from South 168th Street to South 176th Street.

SR 509 ramp closure information 

Thursday, April 23 to the morning of Friday, April 24:

  • 9 p.m. to 5 a.m. – The South 160th Street on-ramp to northbound SR 509 will close overnight. A signed detour will be in place.
  • 9 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 516 ramp closure information 

Thursday, April 23 to the morning of Friday, April 24:

  • 11 p.m. to 3:30 a.m. – The westbound SR 516 on-ramp to northbound Interstate 5 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.