A federal judge will allow Denver Water to continue work on a $531 million project to raise a dam in Boulder County, dealing a blow to environmentalists who had hoped to stop the construction.
However, Senior U.S. District Judge Christine Arguello in her ruling May 29 prohibited Denver Water from filling Gross Reservoir until federal environmental permits can be rewritten by the Army Corps of Engineers.
“There is no evidence that there would be additional environmental injury resulting from completion of the dam construction. In fact, the opposite is true,” Arguello wrote. “There is a risk of environmental injury and loss of human life if dam construction is halted for another two years while Denver Water redesigns the structure of the dam and gets that re-design approved by” the Federal Energy Regulatory Commission. 
FERC is involved because of the hydroelectric plant at the base of the dam.
Denver Water’s general counsel, Jessica Brody, said Friday her agency was pleased the judge recognized the safety issues in leaving the dam half-built.
“We’re relieved that the judge understood and appreciated the safety issues. We are relieved as well that she understood the impact to Denver Water’s customers,” Brody said.
The construction is expected to be completed this year, she said. In the meantime, she said, her agency will move forward in asking a federal appeals panel to rule on whether key environmental permits need to be rewritten, as Arguello has ordered.
If the permits are redone, it could mean that the U.S. Army Corps of Engineers will determine that the metro Denver water provider, which serves 1.5 million people, needs less water from the Fraser River to fill an expanded Gross Reservoir than the original permit authorized.
The judge initially shut the project down April 3, saying that the Army Corps and Denver Water had violated the federal Clean Water Act and the National Environmental Policy Act when the Gross Reservoir expansion permits were issued in 2017.
Save The Colorado, one of the plaintiffs in the case, said Friday morning that it will defend the portion of the Thursday ruling that could prevent or reduce additional diversions from the Fraser River, a key tributary in the Upper Colorado River system.
“Importantly,” said Save The Colorado’s Gary Wockner, “her original 86-page ruling still stands … so they can’t cut trees and they can’t put water in it until it is all resolved.”
How the case progressed
In her April 3 ruling, Arguello said Denver Water had acted recklessly in proceeding with construction in 2022, knowing that important legal questions were being challenged by Save The Colorado, the Sierra Club and others.
The massive construction project to raise the dam 131 feet and triple the capacity of Gross Reservoir has sparked fierce opposition in Boulder County and prompted several legal challenges from Save The Colorado, a group that advocates on behalf of rivers. Though its early lawsuits failed, the group in 2022 won an appeal that put the legal battle back in play. Despite months of settlement talks, no agreement was reached.
Denver Water first moved to raise Gross Dam more than 20 years ago when the water provider began designing the expansion and seeking the necessary federal and state permits. Denver Water has said raising the dam and increasing capacity of the reservoir is necessary to ensure it has enough water throughout its delivery system and to help with future water supplies as climate change continues to reduce streamflows.
After years of engineering, environmental studies and federal and state analyses, Denver received a permit from the U.S. Army Corps of Engineers, and construction began in 2022.
Arguello’s April 3 ruling said, in part, that the Army Corps should have considered whether ongoing climate change and drought would leave the Colorado River and Western Slope waterways too depleted to safely allow transfer of Denver Water’s rights into a larger Gross Reservoir for Front Range water users.
At the same time, she ordered a permanent injunction prohibiting enlargement of the reservoir, including tree removal and water diversion, and impacts to wildlife.
Almost immediately, Denver Water filed for temporary relief from the order, saying, in part, that it would be unsafe to stop work as the incomplete concrete walls towered above Gross Reservoir.
Arguello granted that request, too, allowing Denver to continue work on the dam considered necessary for safety.
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