A state board rejected claims the Goldendale pump-storage energy project in south-central Washington would pollute the Columbia River, affirming the Department of Ecology’s judgment.

The Pollution Control Hearings Board, in a ruling released Jan. 27, upheld a permit issued by Ecology certifying that the project, along the river near Goldendale in Klickitat County, will meet water-quality standards.

The three-member board said testimony from Ecology and the project’s developer, Rye Development, was more persuasive than testimony from the Yakama Nation and three environmental groups.

Rye, on behalf of Copenhagen Infrastructure Partners, a Danish investment firm, proposes what would be Washington’s first large pump-storage project.

Electricity would be generated by releasing water from an upper reservoir to an underground powerhouse. The water would empty into a lower reservoir and be pumped back to the upper reservoir.

Rye promotes the project as an important source of on-demand renewable energy to back up intermittent wind and solar power.

The Yakama Nation, Columbia Riverkeeper, Washington Conservation Action and American Rivers claimed the reservoirs and pipes would leak polluted water into groundwater that would eventually reach the river.

The project’s manager, environmental engineer Dylan Stankus, testified the system was designed not to leak. The lower reservoir, the one closest to the river, would be double-lined, with sand between the layers.

The tribe and environmental groups pointed to an environmental impact statement estimating more than 30 million gallons of water would leak from the project every year.

The figure was an early estimate superseded by subsequent work by Ecology to understand the project, according to the board. The department determined the project would not leak or need a permit to release wastewater,  Ecology manager Loree Randall, who led the review, testified

Even if the reservoirs leaked, the water in them will have to meet water-quality standards, the board noted.

The lower reservoir, approximately 4,000 feet from the river, would be on land once occupied by an aluminum smelter. A lot of water would have to leak to move contaminated groundwater into the river, Ecology’s cleanup site manager, David Johnson, testified.

Board members Michelle Gonzalez, Chris Swanson and Gabriel Verdugo signed the decision.

“We are pleased with this ruling from Washington’s Pollution Control Hearings Board,” Rye Development chief development officer Erik Steimle said in a statement.

“Today, we are one step closer to advancing Washington’s first pumped storage facility and creating a more sustainable and reliable energy future for our region,” he said.

Rye must obtain a license from the Federal Energy Regulatory Commission. The project has passed environmental reviews, but still faces opposition from the Yakama Nation over the project’s impact to off-reservation sacred and historic sites.