TagSR509(117)

This WSDOT discussion document from November 2021 shows a planning map for the SR 509 Puget Sound Gateway Program's new expressway project, spanning from 24th Ave S to S 188th St near Des Moines Creek Park in the City of SeaTac. The map highlights the proposed highway alignment (shown in red) running adjacent to Des Moines Creek Trail Park, identifying wetland areas, contour elevations, and nearby features such as an Amazon warehouse and the Lake to Sound Trail. The project represents a major infrastructure expansion in the SeaTac area that would affect the Des Moines Creek Park corridor and surrounding natural resources.

In February 2021, the Port of Seattle Commission was asked to authorize the purchase of a 14.3-acre strip of former SR-509 highway right-of-way from WSDOT for approximately $3.15 million. The land, located in Des Moines, WA adjacent to the Port's Des Moines Creek West property, was intended to support development near Seattle-Tacoma International Airport. The acquisition aimed to consolidate Port-controlled land in an industrial corridor close to the airport's flight path.

The Washington State Department of Transportation (WSDOT) presented the Puget Sound Gateway Program to the Highline Forum in November 2020, outlining plans to complete SR 509 in King County and SR 167 in Pierce County. The SR 509 project includes creating a new south access point to Sea-Tac Airport, improving freight connections to the ports of Seattle and Tacoma, and reducing congestion on local roads. The program also proposes tolling as a tool for sustainable congestion management.

The SR 518 Corridor Planning Study, published by the Washington State Department of Transportation (WSDOT) in May 2020, examines the stretch of State Route 518 running from SR 509 to Interstate 5 (milepost 0.00 to 3.42) in the Seattle area near Sea-Tac Airport. The study was conducted by WSDOT's Management of Mobility Division to evaluate transportation conditions and identify potential improvements along this key corridor. It was formally approved by WSDOT leadership in November 2019 and includes standard civil rights and accessibility notices in both English and Spanish.

This 2019 WSDOT report analyzes noise barriers along the SR509 Phase 1 highway alignment near the Sea-Tac area, evaluating whether proposed sound walls meet feasibility and cost-reasonableness standards. Wall 3 was rejected because it could not achieve the required 5 dB noise reduction for nearby residents. Wall 4 met the technical noise-reduction threshold but was ultimately rejected because its estimated cost of $111,478 exceeded the allowable budget of $72,254.