UPDATE: Construction on SR 509 Completion Project to begin in late 2019

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The SR 509 Completion Project team announced that they are looking forward to a busy fall:

  • Sound Transit will begin building the first stage of the project in late 2019 as part of their Federal Way Link Extension Project. This coordination will reduce the construction schedule and minimize impacts.
  • Project staff will be at the Des Moines Waterfront Market this Saturday, Sept. 15 to inform the public about what’s next for the SR 509 Completion Project.
  • We’ll be talking with contractors interested in building the SR 509 Completion Project at WSDOT’s regional contracting event at South Seattle Community College on October 2 and the Regional Contracting Forum at McCaw Hall on October 9.
  • The project is continuing real estate acquisitions to provide room for the planned improvements. If you have specific questions about property to be purchased for the SR 509 Project, please contact Susan LeCavalier, the project real estate manager, at (206) 440-4173.

Needs & benefits
Extending SR 509 will ease congestion on I-5 near Tukwila, add a southern access point to Sea-Tac International Airport, and improve service between industrial districts by allowing general purpose traffic and trucks to bypass I-5, SR 99 and local streets.

When finished, SR 509 will become a key component of the Seattle and south King County transportation network. When considered in conjunction with the planned Alaskan Way Viaduct improvements, the project provides a critical north-south corridor alternative to I-5 through Seattle and South King County.

  • Freight connections. Completes critical freight links between the Port of Seattle and key distribution, warehouse and industrial centers in King County.
  • Regional mobility. Reduces traffic congestion on local roads and highways by completing connections between Seattle and the Kent Valley. Provides an alternate route to I-5 in south King County.
  • Airport Access. Provides for a new connection between I-5 and Sea-Tac Airport from the south for both passengers and air cargo.
  • Regional job and economic growth. Supports regional job growth and economic growth associated with the state’s two largest ports.
  • Intelligent transportation. Improves safety and manages congestion with tolling.
  • Advance wetland mitigation. Improves water quality and wildlife habitat by completing environmental improvements in advance of the project.

SR 509 was funded over a 16-year timeline. Based on the funding plan under Connecting Washington, major construction for the first stage would likely occur in 2022-2025, and a second stage would begin in 2026-2029.


  • Connecting Washington: $1,565 million
  • Local Funding: $130 million
  • Toll Funds: $180 million
  • Total funding:  $869 million

Contact [email protected]gov for more information.

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