Smith Diversion Dam Fish Passage

The Walla Walla Basin Watershed Council completed construction of the Smith Diversion Dam Fish Passage project in September 2012. The Smith dam, a grade control sill, is located at river mile 44.9 on the Walla Walla River along the edge of Milton-Freewater. The structure was originally built by the US Army Corps of Engineers in the 1940s as part of the Milton-Freewater Levee flood protection project. Over the last few years a three foot head cut in the river bed migrated up to this structure, creating a fish passage barrier for redband trout, bull trout, juvenile steelhead, and juvenile Chinook salmon during low flows. There was also concern that if the concrete sill collapsed or was undermined, the toe of the flood protection levee could be exposed and vulnerable to erosion. The Walla Walla Basin Watershed Council worked with project partners to secure funding for design, permits, and construction. The WWBWC contracted with GeoEngineers, Inc. for design work and construction oversight, and Partney Construction, Inc. of La Grande completed this in river construction project. A passage notch was cut into the concrete dam and an engineered roughened riffle was constructed immediately below the concrete sill to ensure fish passage at low flows.

Steelhead, Chinook salmon, bull trout, and redband trout will have improved fish passage at low flows once this project is complete. There is also the potential to increase side channel habitat for juvenile salmon and steelhead rearing. Both these improvements will increase spawning success and juvenile survival.