Washington State Department of Transportation (WSDOT)

Thornton Creek Fish Passage Barrier Removal

The existing crossing of Thornton Creek at State Route (SR) 522 was identified as a barrier to fish passage. To address this, the Washington State Department of Transportation (WSDOT) advanced a project to restore fish passage at this location (milepost 2.86) within WSDOT’s Northwest Region. Building on a preliminary hydraulic design, the project refined a final design concept consistent with the WSDOT Hydraulics Manual and fish-passage requirements, with attention to long-term channel stability and performance over the life of the structure. The work supported WSDOT’s obligations under the federal fish-passage injunction, its commitments related to Tribal Treaty Rights, and coordination with tribal fishery managers and WDFW. Correcting the barrier is expected to provide access to approximately 23,215 linear feet of habitat gain while also exploring opportunities to reduce costs, accelerate construction, and improve channel performance over time.