I-90: Snoqualmie Pass East, Hyak to Keechelus Dam Improvements

Location: Kittitas County, WA
Client: Washington State Department of Transportation (subconsultant to URS)

Otak provided leadership in surface water drainage, endangered species habitat and regulatory permitting and mitigation for improvements to a 15-mile segment of I-90, located in one of the world’s largest snowsheds. They observed overland flow conditions on hill slopes, measured stream bed gradient, channel dimensions and bed sediment size and delineated channel migration zones to ensure that new culverts and bridges would be designed to suit natural conditions. Their assessments provided key insights regarding potential effects of stormwater runoff on threatened species such as Steelhead and Bull Trout, and provided project engineers with critical information about the natural complexities of the area.

Related Disciplines