Two local roads in SeaTac close to make way for the new SR 509 Expressway

South 194th Street connection to Des Moines Memorial Drive South will close permanently on July 7. South 192nd Street is scheduled to close for nine months also on July 7

The long-awaited State Route 509 Expressway in south King County is taking shape. Before travelers can move without stopping between South 188th Street and I-5, our construction crews have a lot of work ahead of them at South 192nd and South 194th streets near Des Moines Memorial Drive in SeaTac.

South 194th Street is closing for good

First up: On July 7 crews will permanently close the South 194th Street connection to Des Moines Memorial Drive South. This is because the new expressway is going to be built right where the current intersection is located.

Building the new South 192nd Street bridge

Shortly after South 194th Street is closed, crews will shut down a portion of South 192nd Street for nine months while they build one of five new bridges for the expressway. It’ll be closed just west of Des Moines Memorial Drive.

Right now, South 192nd Street is just a road, but it will become a bridge. The new SR 509 Expressway will go under South 192nd Street. To build the expressway, crews need to dig out the road and transform it into a bridge. South 192nd Street, between Des Moines Memorial Drive South and Eighth Avenue South, will be closed for about nine months starting July 7.

The new South 192nd Street bridge will better serve the needs of the community with wide, ADA-accessible sidewalks.

The new South 192nd Street bridge will better serve the needs of the community with wide, ADA-accessible sidewalks.

Originally, crews planned to build the new bridge before permanently closing the South 194th Street connection to Des Moines Memorial Drive. But closing both at the same time results in:

• Safer detour routes with fewer tricky left turns.
• Keeping Des Moines Memorial Drive South open more often.
• Less dust and dirt from construction vehicles.
• Trucks having the ability to travel during the day instead of at night.

Getting around during construction

While South 192nd Street is closed:

• Cars will be detoured to South 188th Street or South 200th Street using Eighth Avenue South and Des Moines Memorial Drive South.
• Large trucks should use First Avenue South to avoid tight turns at Eighth Avenue South.

If you live or work nearby:

• Driveway access on South 192nd Street will be maintained.
• Expect noise, dust, and vibration during regular work hours (weekdays, 7 a.m. to 5 p.m.)
• Some night work may be necessary (weekdays, 8 p.m. to 6 a.m.).

If you commute through the area:

• Use extra caution through the work area and detour route and expect delays.

If you use the Lake to Sound Trail:

• Expect closures and detours during bridge. construction. Visit our project webpage for updates.

The new South 192nd Street bridge over the future SR 509 Expressway is scheduled to open in early 2026.

Project background

The SR 509 Completion Project in King County is part of the Puget Sound Gateway Program, which also includes the SR 167 Completion Project in Pierce County. Together, these projects complete two of the Puget Sound region’s most critical freight corridors and improve access to I-5, the ports of Tacoma and Seattle, and Seattle-Tacoma International Airport. The SR 509 Completion Project builds a new four-lane expressway between I-5 and SR 509's current end near Sea-Tac Airport, builds new I-5 ramps, improves I-5 interchanges in south King County, and constructs new bridges. When complete, the project will create an important north-south alternative to the congested I-5 corridor between Seattle and south King County.

Keep in touch

The best way to stay up to date on the SR 509 completion project is to sign up for our listserv. Questions? Send us an email at sr509construction@wsdot.wa.gov or give our 24/7 construction hotline a call at 206-225-0674.