SR 509 Completion Project kicks off construction with work along I-5 in south King County

Online open house also launches with details of what’s ahead

KENT – Construction is now underway on a major project to complete the unfinished State Route 509 in south King County, adding 3 miles of new highway that will connect SR 509 to Interstate 5.

Work on this new stage of the SR 509 Completion Project begins in Kent, at the I-5/SR 516 Interchange. Improvements to this busy interchange include extending nearby Veterans Drive to create a new connection to I-5 and the future SR 509 Expressway. These improvements will ease traffic congestion to and from the Kent Valley. The 4-year project includes:

  • Reconstructing the I-5/SR 516 interchange in Kent, with improved access to transit.
  • Extending Veterans Drive under I-5 in Kent to connect to I-5 and the future SR 509 Expressway.
  • Building the first of 3 new miles of SR 509 Expressway between I-5 and 24th Avenue South in SeaTac.
  • Constructing a new South 216th Street bridge with bike lanes and sidewalks over I-5 between SeaTac and Des Moines.
  • Building new ramps that connect I-5 to a new SR 509 Expressway.

In early 2022, work also starts on I-5 at the South 216th Street bridge on the Des Moines/SeaTac border. The 216th Street bridge will be widened and replaced to make room for ramps to the future SR 509 Expressway to pass underneath.

Travelers should expect lane shifts and nighttime lane closures on southbound I-5 this fall. Additional I-5 lane shifts and closures begin in early 2022.

How to learn more

The Washington State Department of Transportation has launched an online open house to provide more detailed information about upcoming construction and the schedules for completing the major activities.

More information is also available in this construction blog.

About the SR 509 Completion Project

The SR 509 Completion Project is an 8-year project to build the remaining 3 miles of SR 509 and connect it from its existing end point in SeaTac to I-5.

Current construction ends in 2025 and will be followed by a final construction project which will build the remaining 2 miles of new SR 509 Expressway and bring new transportation options to the Puget Sound region. The entire SR 509 Completion Project is expected to wrap up in 2028.

The SR 509 Completion Project in King County and the SR 167 Completion Project in Pierce County are managed under the Puget Sound Gateway Program. Together, these projects will improve the movement of freight by connecting the state's largest ports to key distribution centers in King and Pierce counties. Completing these unfinished highways will move freight more efficiently and ease traffic congestion throughout the Puget Sound region.

Learn more in this Puget Sound Gateway Program video.

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