Project Overview

Key Features of the SR 509 Completion Project include:

  • Two lanes in each direction on the new segment of SR 509.
  • Interchange improvements at South 188th Street, 24th/28th Avenue South, I-5, SR 516 and Veterans Drive.
  • Improved southern access to Sea-Tac International Airport via a new interchange between 24th Avenue South and 28th Avenue South.
  • New bridge crossing over I-5 at South 216th Avenue.

  • Additional southbound lane on I-5 from SR 516 & Veterans Drive to South 272nd Street.
  • All lanes on the new portion of SR 509 will be tolled using one electronic toll point.
  • The SR 509 alignment will cross over the Lake to Sound Trail near South 200th Street and South 188th Street.

509 map

Extensive Engagement Helped Inform Design

Since the SR 509 Completion Project was funded, WSDOT has regularly met with the community and stakeholders in the project area. Our outreach efforts to date include:

3 open houses

25 briefings

10 Steering Committee meetings

4 Executive Committee meetings

10 social service provider briefings

2 Funding and Phasing Subcommittee meetings

Use the arrows below to view the project area before and after the construction of the project.

SR 509

sr509 before

sr509 after
SR 516 Interchange

sr516 interchange before

sr516 interchange after
I-5 at S 272nd

sr272 before

sr272 after



SR 509 was funded over a 16-year timeline. The schedule below illustrates the anticipated project design, right of way, and construction. Based on the funding plan under Connecting Washington, major construction for a first stage would likely occur in 2021-2025, and a second stage in 2025-2030. The first stage of construction on SR 509 will need to be closely coordinated with Sound Transit’s Federal Way Link Extension project scheduled to open by 2024.


project timeline