A final environmental assessment and Finding of No Significant Impact point to adding a third hydro unit at the 10.2-MW Black Canyon Diversion Dam in Idaho.
Dam owner the U.S. Department of Interior’s Bureau of Reclamation previously completed an EA and FONSI for the project, on the Payette River, in October 2011 but developed this new EA after receiving data from geological testing conducted in 2012 and 2013.
The final EA analyzes a proposal to add a 12.5-MW generating unit in a new powerplant, with the power produced integrated into the grid to serve 10 irrigation districts in southern Idaho and eastern Oregon and the Shoshone-Bannock Tribes.
In addition, this final EA analyzes:
- Installation of a new penstock and intake structure
- Replacement and relocation of the switchyard to address personnel and equipment safety concerns
- Replacement of the existing administration building, which will be displaced by addition of the third unit
- Control upgrades for the two existing units
In the FONSI, Reclamation selected Alternative B, which would mean adding the third unit. This additional unit will take advantage of water that is being discharged via the spillway, as well as provide operational flexibility when one of the two original units is shut down for maintenance.
Reclamation anticipates this unit will generate an additional $3.56 million in revenue annually.
Most of the project will be funded by Bonneville Power Administration, which markets hydropower generated at Reclamation facilities in the Pacific Northwest. The most recent costs estimate for the project was not available, but a 2013 report indicated Reclamation expected it to cost about US$53 million.
The tentative schedule for this work has construction beginning in January 2017 and being completed in summer 2019.
Black Canyon Diversion Dam was built by Reclamation in 1924 as part of the Payette Division of the Boise Project. It is a multipurpose facility that provides water for irrigation, hydropower, recreation and fish and wildlife resources.