Washington State
Drivers should plan ahead for overnight closures on Des Moines Memorial Drive South in SeaTac from April 4 through the morning of April 7.
The Washington State Department of Transportation will close the roadway nightly from 9 p.m. to 4 a.m. in both directions between South 196th Street and South 194th Street. A signed detour will be in place.
The closures will allow contractor crews to install nine large steel bridge girders. These beams will support a new overpass carrying the future SR 509 Expressway above Des Moines Memorial Drive South.
The work is part of the SR 509 Completion Project, a long-term effort to improve regional mobility and freight access near Seattle-Tacoma International Airport.
Once complete, the project will add three miles of new tolled highway connecting Interstate 5 to South 188th Street. Portions of the project opened in 2025, with the full corridor expected to be completed by 2029.
Drivers should expect delays and consider alternate routes during overnight hours.
Photos of construction work are available on the project’s Flickr page. A 3D video tour is also available on WSDOT’s YouTube page.
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.
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