I-90/Keechelus Dam to Stampede Pass – Phase 2A


Washington State Department of Transportation

Completion Date



Washington State Department of Transportation


Hyak, Washington

Delivery Method

General Contractor



Contract Value

$72 million
1-90/Keechelus Dam to Stampede Pass Phase 2A

I-90 Keechelus Dam to Stampede Pass, Phase 2A enhances a 2.5-mile stretch of I-90 on Snoqualmie Pass, extending from the Keechelus Dam vicinity to the Stampede Pass Interchange (MP 59.50 to MP 62.00). The primary objective is the widening of the existing four-lane highway to six lanes. The construction scope encompasses several key elements, including the establishment of an illuminated chain-up area on the westbound lanes, the installation of new culverts at Unnamed Creek and Townsend Creek, the creation of a wildlife overcrossing near the Price Creek Rest Area Vicinity, the implementation of hydraulic connectivity zones at two designated locations, the installation of concrete barrier and guardrail systems, the integration of Intelligent Transportation Systems (ITS), the development of additional mitigation sites at the Price Creek Mitigation Site, and the construction of new bridges at Unnamed Creek, Price Creek, and Noble Creek.

The overarching goals of the project are to reinforce capacity and enhance safety. This is achieved through the addition of a new lane in each direction, the replacement of concrete pavement, the stabilization of rock slopes, the straightening of the roadway alignment, and the establishment of a new chain-up area. The wildlife crossing component addresses the historical migration path to Keechelus Lake and serves as a critical measure to accommodate wildlife such as elk, deer, and black bears. Importantly, this feature contributes significantly to the reduction of wildlife collisions with traffic.

This project joins the eastern end of an existing Atkinson contract (Phase 1C), which involves widening 3 miles of I-90 from four to six lanes and constructing side-by-side elevated avalanche bridges. A comprehensive traffic control program encompassing both projects was implemented. This approach maximized coordination and reduced costs for the Washington State Department of Transportation.