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Project Scope

What is included in Stage 2?

The SR 509, 24th Avenue South to South 188th Street– New Expressway Project includes the following key features:

  • 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]
  • SR 509 expressway bridge spanning park land and a 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
  • Retaining walls to minimize impacts to nearby wetlands and stream buffers
  • Landscaping, wetland preservation, and environmental rehabilitation activities at Barnes Creek in Des Moines and within the SR 509 corridor in SeaTac
A map of the entire SR 509 alignment
Stage 2 project features are located in Burien, Des Moines, Kent and SeaTac. Click map to enlarge.