Mirabel Dam Modifications for Improved Fish Passage

This project modified an existing water diversion structure (Mirabel Inflatable Dam) to improve fish passage. The project improved attractive flows to a new fish passage structure, eliminating delays in fish passage due to sub-optimal flow conditions, unattractive flow conditions over the Dam and eliminated the need to alter Dam inflation to accommodate fish passage. This project addressed the above goal by installing a new vertical slot fish ladder and fish screen that provides an attractive flow of 65 cubic feet per second (cfs), which is much greater than the previous 25 cfs through the former right bank Denil ladder. Additional attractive flows within the pump intake structure are shunted to the bottom of the ladder for additional attractive flows at approximately 135 cfs. This project improved access for coho salmon to an estimated 462.3 miles of anadromous habitat in the Russian River basin. Upon review, the reported proposed miles made accessible were found to be based a hydrologic layer, which likely exaggerated the miles of anadromous distribution above the dam. The actual miles reported are likely a minimum estimate, but are based on recognized steelhead distribution above the dam.

Improve fish passage.