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WSDOT online open houses

Key Feature: SR 509 I-5 Expressway and ramps

This online open house ran from January 25 to March 5, 2021. While the public comment window is now closed, WSDOT is keeping the information available for viewing. For construction questions, please contact Chris Hoffman, hoffmac@consultant.wsdot.wa.gov

SR 509 I-5 Expressway and ramps

The following section describes some of the key features of the project. The designs presented are conceptual. The design-builder will finalize the schedules and designs, which may vary from the conceptual designs.

Building the first mile of the SR 509 Expressway and the ramps that will connect I-5 to the SR 509 will require major construction in SeaTac. WSDOT’s contractor will:

An aerial image of the new I-5 expressway and ramps
A reconfigured SR 516 interchange, new ramps that provide connections between SR 509 and I-5, and non-motorized improvements will make it easier for people who drive, walk, bike and use transit to travel through the area.

Construction impacts:

Our contractor will develop specific plans for constructing the northbound SR 509 overpass. However, their plans to build an overpass instead of an underpass  reduces impacts to the traveling public. The overpass eliminates the need for I-5 closures and lane shifts that were part of the original designs, which included building I-5 bridges that the new SR 509 would travel under. More specific information about overpass construction will be provided at a construction open house in late 2021 or early 2022.

This artist’s rendering shows how the northbound SR 509 ramp goes over I-5. This design greatly reduces impacts to I-5. In the original design, the ramp went under I-5, which required extensive, long-term traffic shifts during construction.