Rattlesnake Wilderness dams

Removing hazard, restoring watershed function

About the Project

Between 1911 and 1923, 10 dams were built on eight high mountain lakes in Montana’s Rattlesnake Creek headwaters to augment water supply for the City of Missoula. These dams are located deep in the Rattlesnake Wilderness Area, which folds into the Lolo National Forest. After a long legal battle with the Mountain Water Company, the City of Missoula in June 2017 assumed ownership of Rattlesnake Creek Dam, the 10 wilderness storage dams, and all associated water rights. The wilderness dams create significant hazard and are costly to maintain. After removing Rattlesnake Creek Dam in August 2020, the City now turns its attention toward improved management of the obsolete water system upstream.

Montana Fish, Wildlife and Parks completed an assessment recommending removal of eight dams to address watershed hazards, reduce maintenance needs, eliminate non-native rainbow trout species, and re-naturalize the sites to protect their wilderness character. The assessment also recommends rehabilitation of two dams on the largest wilderness lakes so they can provide cold-water releases to Rattlesnake Creek during drought and summer months to manage streamflow and temperatures for the benefit of the community and native fish.

Removing the eight wilderness dams is expected to take at least 10 years and will likely include significant regulatory and logistical challenges given the inherent obstacles of removing dams deep in a wilderness area. A pilot dam decommissioning effort, supported by Open Rivers Fund, will provide a roadmap and build momentum for subsequent removals.

In 2018, the City, Trout Unlimited, and Montana Fish, Wildlife and Parks (MFWP) completed an initial assessment of the best course of action for the wilderness dams. The assessment recommended removing eight dams to address watershed hazards, reduce the City’s maintenance requirements, rid the watershed of non-native rainbow trout species, and re-naturalize the sites to protect their wilderness character. The assessment also recommended rehabilitation of the two dams on the largest wilderness lakes so they can provide a failsafe source of cold water for release into Rattlesnake Creek during drought and summer months to manage streamflow and temperatures for the benefit of the community and native fish.

Removing the eight wilderness dams is expected to take at least 10 years and will likely include significant regulatory and logistical challenges given the inherent obstacles of removing dams deep in a wilderness area. The Open Rivers Fund is supporting Trout Unlimited, in partnership with the City and MFWP, to develop a pilot dam decommissioning effort for one of the wilderness dams to test and refine the permitting process with the US Forest Service. Successful completion of the first dam decommissioning will provide a roadmap and build momentum for subsequent removals.

FACTS AT A GLANCE
Owner: City of Missoula
Size: Range of sizes
Project Cost: TBD
ORF Investment: Pilot dam decommissioning effort to test and refine the permitting process
Miles Opened: N/A
Fish: Federally threatened bull trout, native westlope cutthroat, mountain whitefish, and sculpin


OUTCOMES
  • Reduce the City’s operations and management costs
  • Eliminate City liability concerns related to deteriorating dams
  • Re-naturalize the sites to maintain wilderness character of the river
  • Support basin-scale fishery restoration efforts in the middle and upper Clark Fork River by providing important spawning and juvenile habitat for ESA-listed fluvial bull trout, westslope cutthroat trout, mountain whitefish, and sculpin
  • Eliminate the source of non-native rainbow trout in the watershed

Project Partners

City of Missoula

County of Missoula

Trout Unlimited

Montana Fish and Wildlife and Parks

U.S. Forest Service

Clark Fork Coalition