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Corps Looks to Add Another Turbine to Dworshak Dam by Eric Barker Moscow-Pullman Daily News, August 22, 2025

Project will be a long process,
not expected to be completed by 2036

The Army Corps of Engineers and Bonneville Power Administration said Thursday they intend to add a fourth power generating unit to Dworshak Dam.

According to a Corps news release, the hydroelectric turbine would generate 250 to 300 megawatts of electricity, enough to power more than 200,000 homes. It would also reduce the amount of water spilled at the dam during flood control operations and thereby lessen the build up of dissolved gas that at high levels can harm salmon and steelhead.

The dam just upstream from the mouth of the North Fork of the Clearwater River has three existing hydroelectric turbines. But the structure was built to accommodate up to six. Congress authorized the concept of an additional turbine in 2014, a feasibility study was completed in 2019 and design work began this year.

According to the news release, the agency will start writing an environmental impact statement next year.

"The addition of a fourth hydropower unit at Dworshak will provide significant power generation and grid stability benefits as well as risk reduction for both generation and environmental concerns," said Kara Morgan, senior project manager for the Corps, in the news release. "We're in the early design phase now, and we anticipate 3-4 years of design, followed by 5-7 years of construction, with completion expected by Fiscal Year 2036."

A new turbine would also add redundancy in case an existing turbine comes off line and may alter the way the agency refills the dam.

Dworshak Dam was constructed to add flood control to the Columbia River system. But it also provides other services that include power generation, and mitigating water temperature in the lower Snake River to aid the migration of juvenile and adult salmon and steelhead, many of which are protected under the Endangered Species Act.

Operation of the dam also affects recreation. Changing flows can impact fishing and water quality. A mix of federal, state and tribal governments have worked out a complicated set of protocols that govern its operation to lessen the impacts on recreation and fish health. For example, rules dictate ramp rates -- the speed at which the river is allowed to rise and fall.

Dworshak Reservoir is drafted in the late winter and early spring to make room to capture spring runoff. The Corps prefers to lower the reservoir by running water through the turbines. But during high snow years and high spring runoff, some of the water is released over spillways. As it plunges into the river, it creates high levels of gas that can harm migrating fish and fish in Dworshak National Hatchery that draws some of its water from below the dam.

Water is also sometimes spilled in the summer, as fisheries agencies call for cool water from the reservoir to mitigate high water temperatures downstream. From July to the middle of September, Dworshak Reservoir is lowered 80 feet by the water temperature mitigation program.

"In addition to improving reliability of generation from Dworshak, there are significant water quality benefits," said Doug Knapp, BPA's project representative to the Walla Walla District, in the news release. "During spring runoff and summer temperature augmentation, the additional unit greatly reduces the need to spill water, which adds dissolved gas to the river. Being able to pass water primarily through the powerhouse will improve water quality and be a significant benefit to the ecosystem."

The environmental impact statement would examine the pros and cons of adding a new turbine. Consultation with the U.S. Fish and Wildlife Service and NOAA Fisheries would examine how another unit would affect protected salmon and steelhead.

According to the news release, because the dam was constructed to accommodate additional turbines, much of the infrastructure to do so is already in place.

"Many systems in the existing powerhouse will only need to be expanded to accommodate the new unit," Morgan said.

Related Pages:
Corps, State to Partner in Dam Studies by Eric Barker, Lewiston Tribune, 11/5/24