People driving should expect nighttime lane and ramp closures on I-5 and SR 509 in Kent and SeaTac Monday, July 27 to the morning of Friday, July 31, the Washington State Department of Transportation (WSDOT) announced.
The lane closures on I-5 will allow WSDOT contractor crews to build barriers that help separate traffic and improve safety.
The ramp closures on SR 509 will allow crews to perform electrical work.
This work is part of the SR 509 Completion Project.
I-5 lane closure information
Monday, July 27 to the morning of Friday, July 31:
- 11 p.m. to 6 a.m. – Up to three lanes of southbound I-5 will close nightly from SR 516 (Exit 149) to South 272nd Street (Exit 147).
SR 509 lane closure information
Wednesday, July 29 to the morning of Thursday, July 30:
- 9 p.m. to 5 a.m. – The South 188th Street ramp to northbound SR 509 will close overnight. A signed detour will be in place.
Thursday, July 30 to the morning of Friday, July 31:
- 9 p.m. to 5 a.m. – The southbound SR 509 off ramp to South 188th Street 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 in SeaTac and South 188th Street near the south end of Sea-Tac Airport. Crews are building the new expressway in stages. The first stage, completed in 2022, built a new bridge on SR 99 in SeaTac. The next stage, which opened in summer 2025, built the first mile between I-5 and 24th Avenue South. That stage also included the new Veterans Drive tunnel in Kent near the SR 516 interchange.
Crews are now working on the final stage which builds the remaining 2 miles of the expressway between 24th Avenue South and South 188th Street in SeaTac. The entire expressway is scheduled to open to the public in 2028.
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 projects complete critical missing links in Washington’s highway and freight network.
