SR 509/24th Avenue South to South 188th Street New Expressway – What’s not included in Stage 2?

Stage 1a

The first stage of the SR 509 Completion Project built a new SR 99 bridge in SeaTac below the Link light rail elevated guideway and above the SR 509 roadway. The SR 99 bridge opened to traffic in July 2022.

Stage 1b

This stage of the SR 509 Completion Project, which is currently in progress, builds the first mile of new tolled expressway between I-5 and 24th Avenue South, new I-5 ramps, new interchanges, a tunnel under I-5 and a new South 216th Street bridge. Project photos and visualizations are available on our Flickr page and the SR 509 Expressway interactive map.

Aerial view of the first mile of the new SR 509 expressway and I-5 connections — The first mile of the new SR 509 expressway and I-5 connections are being built
through the SR 509 Stage 1b contract

What is the Puget Sound Gateway Program?

The Puget Sound Gateway Program includes the SR 509 Completion Project in south King County and the SR 167 Completion Project in Pierce County. Together, these improvements will enhance the state’s economic competitiveness, both nationally and globally, connecting the state’s largest ports to key distribution centers in King and Pierce counties.