The SR 509 Completion Project extends State Route 509 from 24th Avenue South to South 160th Street near Sea-Tac Airport, adding new interchanges, roundabouts, and connections to southbound I-5 and toward Seattle. Key features include a new interchange at South 188th Street with a shared-use path and Lake to Sound Trail access, as well as a South 160th Street interchange with noise walls to protect nearby residents. The project also includes wetland mitigation sites and infrastructure improvements along the Des Moines Memorial Drive corridor.Open full document
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This document presents the SR 509 Completion Project, showing a map of the new highway corridor from 24th Avenue South to South 160th Street near Sea-Tac Airport. It includes rendered views of two planned interchanges: the SR 509/South 160th Street Interchange featuring roundabouts and noise walls, and the SR 509/South 188th Street Interchange featuring a new shared-use path and the last exit before a toll. The project connects to southbound I-5 and passes through the communities of Burien, SeaTac, and Des Moines.