The Mill Creek flood control channel presents depth and velocity barriers for summer steelhead, spring chinook, and bull trout. A support pier in the channel for an over 100-year old bridge at 5th Avenue created an additional hydraulic barrier.

Several projects since 2011 have incrementally improved passage in the two-mile long flood control channel by adding resting pools and adding roughened concrete to reduce velocity.

The bridge’s support pier occupied space in the channel that prevented the fish passage treatment. However, the City of Walla Walla decided to remove the bridge and replace it with a pedestrian bridge during the late design phase of the project.

In partnership with the City of Walla Walla and Walla Walla County, Tri-State Steelheaders removed the bridge and completed passage improvements to 1,200 feet of the flood control channel, resulting in 85% of the two-mile concrete channel treated for fish passage.

The result of the project is improved depth and velocity conditions for adults returning to spawn, and for juveniles out-migrating in spring. Project funding was provided by two grants from the Brian Abbott Fish Barrier Removal Board, one grant from Salmon Recovery Funding Board, with matching funds from City of Walla Walla.

Photo of completed bridge by Dillon Crawford, City of Walla Walla. Photos of construction by Brian Burns, Tri-State Steelheaders.