WSDOT announces nighttime road closures for SR 509 project

The Washington State Department of Transportation (WSDOT) has announced several nighttime road closures in South King County from August 31 to the morning of September 4. These closures are part of the State Route 509 Completion Project.

On South 200th Street in SeaTac, nightly closures will occur between 8 p.m. and 5 a.m. from 18th Avenue South to just east of the Des Moines Creek Trail. This final week of closures allows crews to move large trucks to transport soil for the new expressway.

Additionally, nighttime lane closures will affect I-5. From 10 p.m. to 6 a.m., up to two southbound lanes will close nightly between SR 516 (Exit 149) and South 272nd Street (Exit 147) to facilitate drainage work.

The SR 509 Completion Project is building a three-mile tolled highway between I-5 and South 188th Street. The final two miles of the project are currently scheduled to open to traffic in July 2028.