Online open house offers first glimpse of future State Route 509 expressway using 3D model

SEATAC – Members of the public are invited to an online open house to learn more about current designs and planning for the final stage (Stage 2) of the State Route 509 Completion Project in south King County, which includes construction of a new four-lane, three-mile SR 509 expressway. The online open house will also include the release of a 3D video tour of the full project, modeled from current designs.

The Washington State Department of Transportation's (WSDOT) $1.1 billion SR 509 Completion Project extends the highway from where it currently ends at the southeast corner of Sea-Tac International Airport to Interstate 5, and includes project features in Burien, Des Moines, SeaTac and Kent. Stages 1a and 1b of the project are currently under construction. Stage 2 construction is expected to start in late 2024 and wrap up by 2029.

WSDOT's SR 509 spring online open house presents conceptual designs for Stage 2 project features and provides the public with an opportunity to comment and sign up for ongoing project updates. The online open house is available in Arabic, simplified Chinese, English, Somali, Spanish, Tagalog and Vietnamese.

The improvements detailed in the online open house include:

  • Two miles of new SR 509 expressway between 24th Avenue South and South 188th Street (Des Moines/SeaTac)
  • Reconfigured SR 509 interchanges at South 160th Street and South 188th Street (Burien/SeaTac)
  • New South 192nd Street bridge over the new SR 509 expressway (SeaTac)
  • New SR 509 bridge over parkland and stream south of South 200th Street (SeaTac)
  • New southbound auxiliary lane on I-5 between the SR 516 interchange and South 272nd Street (Kent)
  • Increased multi-modal access and safety features on local streets and trails (Burien/Des Moines/SeaTac)
  • Two new noise walls near South 160th Street in Burien and extension of one existing noise wall alongside I-5 in Kent
  • Landscaping, wetland preservation, and environmental rehabilitation activities at Barnes Creek in Des Moines and within the SR 509 corridor in SeaTac

SR 509 spring online open house information


The online open house runs from Monday, May 23, to Wednesday, June 22, when it closes for comments.


Online, at:
Free, temporary internet access is available to those who do not have broadband service in locations throughout the state. To find the nearest Drive-In WiFi Hotspot visit:


The online information is available 24/7.

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 and Move Ahead Washington (PDF 172KB) accounts, federal grants, local contributions and future toll revenues.

8,683 animals crossed the Snoqualmie Pass East Project area

as recorded by WSDOT and partners in 2020 and 2021.

46% increase in Amtrak Cascades ridership to 251,000 passengers

in 2021 compared to 172,000 in 2020.

Nine wetland and stream mitigation sites across 32.7 acres added

to our monitoring program in 2021 to help offset climate change impacts.