A federal appeals court to finish its $600 million Gross Dam expansion project, reversing a lower court’s order that had left the nearly two-decade-old project’s final stages in limbo.
The unanimous opinion from a three-judge panel of sided with the U.S. Army Corps of Engineers against a coalition of environmental groups that had opposed the project and sued to stop it in 2018. The Corps is the federal agency that approved the expansion of Gross Reservoir.
The appellate judges wrote that the Corps had reasonably concluded that it couldn’t quantify the impact of climate change on the expanded reservoir and the Colorado River Basin, the source of much of the reservoir’s water. They found that the agency had adequately considered alternative projects.
“In the end, the Environmental Groups ask us to substitute our judgment for the Corps’s,” Judge Timothy Tymkovich wrote in the panel’s opinion. “They point out scientific studies that, in their view, rebut the Corps’s reading of the scientific literature and ask us to opine on what the scientific research establishes. But our job is not to second-guess the Corps’s assessment as long as it rests on a reasoned basis.”
The ruling means that the project, for which Denver Water first sought permits in 2003, can finally be completed. Construction, which began near Nederland in 2022, has continued while the legal challenge played out, with expansion work on the dam largely completed in June.
But work was halted briefly in 2024, six years after the environmental groups sued to stop it. A U.S. District Court judge initially blocked construction but then allowed it to continue — albeit without allowing Denver Water to divert the water needed to triple the reservoir’s storage, as intended. The project has been in limbo ever since.The planned expansion will increase the reservoir’s capacity to 120,000 acre-feet from 42,000 acre-feet, enough to provide water for roughly 156,000 households for a year. The utility provides water for 1.5 million people in metro Denver, and it had argued that it needed to expand the reservoir to ensure it could continue delivering water if its southern supply system, which includes most of its reservoirs, was impacted.
In a statement provided by spokesman Todd Hartman, Denver Water said it was pleased that the appellate court agreed that the permits were lawfully granted and that Denver Water could complete the project.
“An expanded Gross Reservoir is vital to the future of the Denver region, giving Denver Water far greater ability to flexibly manage constrained water supplies amid the growing risks of catastrophic wildfire and weather extremes that accompany the challenges of drought and climate change already upon us,” the utility said.
Gary Wockner, the director of Save the Colorado, which sued to block the project, said in a statement that it was “nonsensical to be putting more straws in, and further draining, the Colorado River at this point in history.”
He did not immediately respond to a request for comment on whether the opponents would seek a further appeal.
The environmental groups had argued that the Corps failed to evaluate how climate change would impact the Colorado River, whose water is diverted to feed the reservoir through a tunnel under the Continental Divide.
The Corps had noted that climate change may impact water diversions to the reservoir, the appellate judges wrote, but the agency was also reasonable in arguing that it couldn’t quantify or model those effects.
“That the law allows it to happen doesn’t make it right, it just makes it legal,” Wockner said of the project. “I saw something wrong, I stood up, spoke out and took action. It was the right thing to do, and I would do it all over again.”
The project raised the dam by 131 feet, bringing it to 470 feet tall, in a bid to secure more water storage capacity for the reservoir. Denver Water officials previously estimated to The Denver Post that the project needed an additional year of work before it would be fully completed.
As the litigation filtered through the federal court system, a number of outside groups weighed in.
Other water utilities in the state urged the appellate court to allow the project to continue, while more than two dozen former officials from the Environmental Protection Agency sided with the earlier ruling that ordered the permitting process to be undertaken again.
