About the Project

The Clark Fork River flows from the Northern Rockies through western Montana and Idaho and drains into the upper Columbia River system. It provides abundant recreational, economic, and cultural resources to the community, and vital habitat and migration corridors for fish and wildlife.

The Grass Valley Irrigation Diversion Dam, located 16 miles northwest of Missoula, Montana, was built on the Clark Fork River in 1905 to irrigate about 4,250 acres in the Frenchtown area. The diversion system includes an eight-foot-high, channel-spanning concrete and wooden plank dam and a 14.5-mile-long canal that carries diverted water to surrounding land.

The dam and unscreened canal are a major problem for fish passage and entrain an estimated 10,000 fish annually. The aging structure also poses operational safety risks to dam maintenance workers and is hazardous to boaters.

The dam’s owner, Grass Valley French Ditch Company, and Trout Unlimited are partnering to develop plans to remove the dam and modernize the irrigation infrastructure to improve fish migration, eliminate fish entrainment, and minimize safety hazards. Successful completion of this project will sustain community enthusiasm for dam removal projects in the region, provide a model for working with rural agricultural districts, and offer an opportunity for citizen scientists to collect valuable watershed monitoring data. This project will also add to miles recently opened by other Open Rivers Fund projects on the Upper Clark Fork River and Rattlesnake Creek, all part of a larger effort to restore fish passage and modernize water infrastructure in the region.