Local Information

Public invited to learn about SR 509 improvements coming to King County at online open house

Tuesday, January 26, 2021 - 08:00

Laura Newborn, communications, 206-639-8577

SEATTLE – The public is invited to an online open house to learn more about the next stage of construction for the SR 509 Completion Project in south King County. The improvements include a mile of new highway and new connections to and from Interstate 5.  

Guy F. Atkinson Construction, the Washington State Department of Transportation’s design-build contractor on this project, is starting a year-long design phase. A design-build contractor completes final design and construction under one contract. Construction is expected to start in 2022 and wrap up in 2025.

WSDOT’s online open house explains the improvements to come and gives the public opportunities to comment before the final design is complete.

Translated versions are also available in Spanish, simplified Chinese and Vietnamese, and can be accessed at the top of the online open house webpage.

Open house information

The online open house runs through Friday, March 5, 2021, when it closes for comment.

Due to COVID-19 restrictions, information is available to view online only. Free, temporary internet access is available to those who do not have broadband service in locations throughout the state.

The online open house contains information on the next stage of construction for the SR 509 Completion Project. The improvements include:

Ahead - completing SR 509  

The last two miles of new SR 509 Expressway between SR 509’s current end point in SeaTac and 24th Avenue South will be built under a future contract, along with a southbound I-5 lane between SR 516 and South 272nd Street. The final stage of SR 509 construction work is expected to start in 2024 and end in 2028.   

About the Puget Sound Gateway Program

The SR 509 Completion Project in King County and the SR 167 Completion Project in Pierce County are part of WSDOT’s Puget Sound Gateway Program. Both projects will complete essential connections to the ports of Tacoma and Seattle to move people and goods more reliably through the region.

The Puget Sound Gateway Program was authorized by the Washington State Legislature in 2015. Funding comes from WSDOT’s Connecting Washington account, federal grants, local contributions and future toll revenues.


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