Public can learn about construction coming to SR 509 in south King County

Online open house includes images of new expressway, information on how work will affect travel through area

SEATAC – People interested in learning more about the State Route 509 expressway construction work planned in SeaTac, Burien, Kent and Des Moines can visit an online open house through Friday, Oct. 25. 

Contractor crews working for the Washington State Department of Transportation have begun work on the final stage of the SR 509 Completion Project. This fall, crews will begin excavating the remaining 2 miles of the expressway between 24th Avenue South and South 188th Street in SeaTac. The first mile of the new tolled expressway, located between Interstate 5 and 24th Avenue South, is already under construction and scheduled to open in 2025 as part of Stage 1b of the project.

The online open house breaks down the work by different areas and neighborhoods, making it easy for people to find information, graphic visualizations and maps for the construction most likely to affect them.

SR 509 Completion Project open house information

When: Wednesday, Sept. 4 – Friday, Oct. 25

Where: engage.wsdot.wa.gov/sr-509-expressway

Details: In addition to English, the online open house is available in Spanish, Vietnamese, Simplified Chinese, Somali, Pashto, Amharic and Khmer.

Visitors will also have an opportunity to submit comments and questions.

Free WiFi access

Free WiFi access is available at several locations for people who do not have broadband access but wish to visit the online open house:

  • Valley View Library: 17850 Military Road S., SeaTac
  • Des Moines Library: 21620 11th Ave. S., Des Moines
  • Burien Library: 400 SW 152nd St., Burien
  • Tukwila Library: 14380 Tukwila International Blvd., Tukwila

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 currently under construction between I-5 and 24th Avenue is scheduled to open in 2025. The final stage will build the remaining 2 miles of the expressway between 24th Avenue South and South 188th Street. The entire project is planned for completion by 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. Combined, the two completion projects finish critical missing links in Washington’s highway and freight network.

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registrations in Washington in 2023, up from 114,600 in 2022.

87 wetland compensation sites

actively monitored on 918 acres in 2023.

25,000 safe animal crossings

in the Snoqualmie Pass East Project area since 2014.