• Original Reporting
  • Sources Cited
Original Reporting This article contains new, firsthand information uncovered by its reporter(s). This includes directly interviewing sources and research / analysis of primary source documents.
Sources Cited As a news piece, this article cites verifiable, third-party sources which have all been thoroughly fact-checked and deemed credible by the Newsroom in accordance with the Civil Constitution.
Ellen Malan, of Denver, relaxes at Gross Reservoir outside Boulder on July 1, 2019. Denver Water is planning a major expansion of the reservoir that will increase height of the Gross Reservoir Dam by 131 feet and water storage by 77,000 acre-feet. Local residents and environmental groups are fighting against the expansion due to concerns about environmental impacts and the lack of conservation efforts. (Chris Schneider, Special to The Colorado Sun)

A federal appeals court gave new legal life to opponents of Denver Water’s major expansion of Gross Reservoir Dam in western Boulder County, while the county’s commissioners officially protested to federal hydropower authorities that construction is ruining neighbors’ lives. 

The 10th U.S. Circuit Court of Appeals said Friday an alliance of advocacy groups has the right to challenge the expansion’s numerous environmental permits from the Army Corps of Engineers in U.S. District Court, rather than through a federal hydropower review with fewer chances to object.

Opponents say the proposed expansion would add 900,000 cubic feet of concrete, “effectively tripling the size of the reservoir,” damaging both local environmental resources and stripping more water from Colorado River tributaries across the Continental Divide. Denver Water wants a bigger pool to store rights to Fraser River water that is pumped under the mountains and comes down South Boulder Creek to the dam. 

The environmental coalition, with the nonprofit Save the Colorado as lead plaintiff, may now seek an injunction to stop construction or demand more concessions from Denver Water on spending money to protect the environment. “We are considering all options,” Save the Colorado founder Gary Wockner said. 

“This important victory will now allow us to prove in court that the Clean Water Act permit for this ill-advised and untenable water grab was unlawfully issued,” Daniel Estrin, general counsel and advocacy director for Waterkeeper Alliance, said in a press release. The Colorado River risks “death by a thousand cuts,” as the basin faces “unsustainable demand, prolonged drought, and runaway climate change, and cannot afford to be further drained to fill another enormous reservoir,” Estrin said. The coalition includes the Sierra Club, WildEarth Guardians and others. 

Denver Water spokesman Todd Hartman said Tuesday the utility is reviewing its options. “No additional comment at this time.” 

Boulder’s three county commissioners, meanwhile, sent a protest letter to the Federal Energy Regulatory Commission that took over approvals of the Denver Water expansion because of a federally licensed hydropower project inside the dam. 

The commissioners had begrudgingly agreed to step out of Denver Water’s way on permitting, in exchange for millions of dollars in mitigation for construction damage and destruction of forests and habitat from the expanded dam and reservoir. 

The Daily Sun-Up podcast | More episodes

“Since construction on the project began in April, the county has received daily complaints from area residents about the noise, industrial lighting, truck traffic, road impacts, public safety, wildfire concerns, and impacts to wildlife from Denver Water’s operations 24 hours a day, 7 days a week. We have grave concerns about the impact the project is having on the daily lives of our residents,” the commissioners wrote on county letterhead, to Federal Energy Regulatory Commission Chairman Richard Glick.

Round-the-clock noise, unpredictable daily rock blasting and disrupted Colorado 72 traffic are only some of the problems plaguing 1,000 homes in the area, the commissioners said, noting that Boulder County gets none of the water from the expanded reservoir. Denver Water serves other communities with the water, and has said it needs the extra storage to balance a supply system currently concentrated in south metro Denver. 


The concessions Boulder County received for greenlighting the project are no replacement for government oversight the county should wield, the letter said. 

“We strongly urge you to personally visit Denver Water’s construction site and see the devastation it is having on the community and the environment,” they wrote the FERC chairman. Denver Water responded that the agency has worked with the community around the dam for years before the project started, and made a number of changes to accommodate concerns.

“We continue to listen and adapt our practices based on local feedback, and will do so throughout the life of the project,” Hartman said. “And while we respectfully disagree with some of the characterizations in the commissioners’ letter, we certainly take these and all comments to heart and look forward to continuing to work with Boulder County and local residents to address and alleviate the issues cited.”

Boulder County settled for $10 million in mitigation last year, with Denver Water putting up the fund to compensate for noise, light and dust impacts on reservoir neighbors, trading land to expand Walker Ranch Open Space, and paying for South Saint Vrain Creek wildlife improvements. In exchange, Boulder County accepted Denver Water arguments filed in federal court in 2021 that the expansion is exempt from county review. 

Denver Water’s own legal action last year had accused Boulder County of slowing down the project and said Denver already had the federal permits it needed because power generation at the base of Gross Dam is federally regulated. The commissioners heard a volume of public opposition, and warned of the project’s potential damage themselves, but concluded a deal was better than losing altogether in federal court.

Michael Booth

Michael Booth is a Colorado Sun reporter covering health, health policy and the environment. Email: Twitter: @MBoothDenver