Replacing four large-scale federal hydroelectric dams on the lower Snake River in Washington state with zero- and low-carbon alternatives could cost public power customers of the Bonneville Power Administration $11.2 billion to $77 billion, according to a new report released by the agency.

The analysis, conducted by research firm Energy and Environmental Economics for the agency, adds cost estimates to ongoing considerations over whether to breach the dams to restore wild salmon and steelhead in the Columbia River Basin. It includes several scenarios for replacing roughly 3,500 MW of total capacity and approximately 2,300 MW of firm peaking capacity at the Lower Granite, Little Goose, Lower Monumental and Ice Harbor dams in eastern Washington.

"Replacing the four lower Snake River dams while meeting clean energy goals and system reliability is possible but comes at a substantial cost, even assuming emerging technologies are available," said the report, released July 12.

Five of six scenarios range between $11.2 billion and $19.6 billion in total cost for 2,300 MW to 4,300 MW of replacement resources, including various mixes of wind, solar, batteries, energy efficiency, demand response, hydrogen- and natural gas-fired generation and advanced nuclear reactors. That could hike retail electric rates between 8% and 18% by 2045, compared with current average rates in Washington and Oregon of about 8.5 cents per kWh, according to the report.

"Most of our scenarios do utilize new technologies that are not yet commercial, specifically hydrogen-enabled combustion turbines," Arne Olson, a senior partner at Energy and Environmental Economics, known as E3, said during a July 12 presentation to the Northwest Power and Conservation Council. "Those turned out to be a pretty key technology across all of our cases."

The sixth scenario does not rely on any new combustion resources and instead would vastly overbuild renewables, including 10,600 MW of new wind capacity and 1,400 MW of solar. That would increase the total cost of replacement, not including actual breaching of the dams, to between $42 billion and $77 billion, and boost rates 34% to 65%, according to the study.

"As the region continues to embrace the health and cost-savings of a decarbonized power sector and to further enhance its supply of clean energy, the E3 study can help inform long-term planning decisions, including to limit the impact to ratepayers," Kathleen Hogan, principal deputy under secretary for infrastructure at the U.S. Energy Department, said in a July 12 statement.

'Crucial moment' for fish

A separate draft report from the National Oceanic and Atmospheric Administration, dated July 11, explored actions needed to make progress toward rebuilding sustainable fish stocks in the Columbia River Basin. Among the options explored is breaching one or more lower Snake River dams.

Both reports resulted from an interagency initiative seeking to restore salmon and steelhead populations in the Columbia River and its tributaries while meeting state and federal clean energy targets.

Two years ago, a federal environmental impact statement called for keeping the lower Snake River dams, coupled with operational changes to help salmon recovery.

"Business as usual will not restore the health and abundance of Pacific Northwest salmon," Brenda Mallory, chair of the White House Council on Environmental Quality, said in a July 12 statement. "We need a durable, inclusive, and regionally crafted long-term strategy for the management of the Columbia River Basin."

"We are at a crucial moment for salmon and steelhead in the Columbia River Basin when we're seeing the impacts of climate change on top of other stressors," added Janet Coit, assistant administrator for NOAA Fisheries.

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