The Federal Energy Regulatory Commission’s Office of Energy Projects staff have reviewed Clark Canyon Hydro LLC’s application for a license for the proposed Clark Canyon Dam Hydroelectric Project, to be located at the U.S. Bureau of Reclamation’s Clark Canyon Dam on the Beaverhead River near the city of Dillon, Beaverhead County, Montana.
FERC on June 23 put out for comment for 30 days an environmental assessment (EA) analyzing the potential environmental impacts of the project. The EA concludes that constructing and operating the project, with appropriate environmental protective measures, would not constitute a major federal action that would significantly affect the quality of the human environment.
On Nov. 23, 2015, Clark Canyon Hydro filed an application to construct and operate the 4.7-MW Clark Canyon Dam Hydroelectric Project. The proposed project would occupy a total of 62.3 acres of federal land managed by the U.S. Bureau of Reclamation and the U.S. Bureau of Land Management.
Reclamation’s Clark Canyon Dam and Reservoir is a flood control and water conservation facility located at the head of the Beaverhead River in southwestern Montana. Clark Canyon Dam was completed in 1964 as part of Reclamation’s PickSloan Missouri River Basin Program, East Bench Unit. It is managed to provide irrigation storage, flood control, and recreation opportunities.
The proposed Clark Canyon Dam Hydroelectric Project would use the existing dam, reservoir, intake and outlet works, and stilling basin. The proposed project would involve the installation of a new 360-foot long, 8-foot diameter steel lining within Reclamation’s outlet works from the existing gate chamber to the stilling basin. At the river end of the liner, a trifurcation would separate flows into two 8-foot-diameter, 35- foot-long steel penstocks leading to a new powerhouse and a new 10-foot long, 8-foot diameter steel outlet pipe that would discharge into the stilling basin through a fixed cone valve.
The 46-foot by 65-foot concrete powerhouse would be located at the toe of the dam adjacent to the stilling basin and contain two 2.35-MW vertical Francis-type turbine/generator units, for a total installed capacity of 4.7 MW.
The project would operate in a run-of-release mode, meaning the project would operate only using flows made available by Reclamation in accordance with its standard practices and procedures; thus project operation would not affect storage or reservoir levels. The project would be operated automatically, but an operator would be on site daily. Power generation would be seasonally dictated by Reclamation’s operations. The proposed project would generate up to 15,400 megawatt-hours (MWh) annually.
The project includes a 4.16-kV buried transmission line from the powerhouse to a substation containing step-up transformers and switchgear located 1,100 feet downstream of the powerhouse, and a 7.9-mile-long, 69-kV overhead transmission line extending from the substation to the Peterson Flat substation (the point of interconnection).