Colorado’s largest water provider must stop construction on a $531 million dam expansion already underway in Boulder County after a federal judge found that assessments of how the project would impact the environment were flawed.
U.S. District Court Judge Christine Arguello in an order late Thursday blocked Denver Water from enlarging Gross Reservoir east of Nederland until major federal environmental permitting processes are redone.
The judge found that allowing the reservoir expansion to continue without redoing the permits would cause irreparable environmental damage that cannot be compensated for with monetary payments. That harm would outweigh any financial costs Denver Water would incur from halting construction, she wrote.
“Environmental injury is often the very definition of irreparable harm — often permanent or at least of long duration,” Arguello wrote. “All parties agree that there will be environmental harm resulting from completion of the Moffat Collection System Project, including the destruction of 500,000 trees, water diversion from several creeks, and impacts to wildlife by the sudden loss of land.”
Denver Water, which provides water to 1.5 million people in metro Denver, said in a lengthy statement Friday evening that it will appeal the ruling, seek an immediate stay of the order halting work, and “do everything in its power to see this project through to completion.”
“We view this decision as a radical remedy that should raise alarm bells with the public, not only because of its impacts to water security in an era of longer, deeper droughts, catastrophic wildfire and extreme weather, but because it serves as an egregious example of how difficult it has become to build critical infrastructure in the face of relentless litigation and a broken permitting process,” Denver Water said in its statement.
Denver Mayor Mike Johnston said in a statement that he found the order to stop work on the dam “deeply concerning.” The utility said the project is 60% complete.
“The completion of Denver Water’s Gross Reservoir Expansion Project means that Denver and its surrounding communities will have the necessary water security for years to come,” Johnston said. “…I am hopeful that Denver Water can get back to work and complete this critical project.”
Project fought by environmental groups
The order is a huge victory for environmental groups that for years have opposed the controversial project. A coalition of environmental groups first filed suit in 2018 to stop the expansion of the reservoir, which they say would harm the health of the Colorado River system — where the reservoir’s water is sourced.
“Denver Water rolled the dice with ratepayers’ money, which was a mistake,” Gary Wockner of Save the Colorado, the lawsuit’s lead plaintiff, said in a statement. “We remain open to negotiations to find a mutually agreeable path forward.”
Denver Water planned to raise the dam’s height by 131 feet. When completed, the expanded dam would triple the reservoir’s capacity from 42,000 acre-feet to 120,000 acre-feet — enough water to serve approximately 156,000 additional households.
The utility began the permitting process for the project in 2002 and started construction in 2022. The Federal Energy Regulatory Commission has ordered Denver Water to finish the expansion by 2027.
Already, workers have partially deconstructed the existing dam, dumped fill material and poured concrete for the expansion. Denver Water temporarily halted construction for the winter season in November and recently resumed work, with concrete placement set to begin Thursday, spokesman Todd Hartman said.
The judge’s preliminary injunction orders Denver Water to halt construction on the dam until a future hearing at which engineers can explain how much additional construction is needed to make the partially built dam safe and structurally sound. She will then issue a permanent injunction dictating how much more construction will be allowed.
“Leaving the project incomplete creates ongoing safety and water supply issues, as Denver Water cannot fill the reservoir to capacity during construction and, as we have testified to the judge, the original gravity dam has been deconstructed and its foundation excavated, exposing steep rock slopes that depend on bolts to temporarily shore them up,” Denver Water said in its statement.
Violations of federal environmental law
Arguello in October found that the U.S. Army Corps of Engineers violated the Clean Water Act and the National Environmental Policy Act when approving permits for the construction of the dam. Arguello said the Corps failed to sufficiently consider other options that could be less environmentally damaging than dam expansion and, in her ruling Thursday, she said the Corps’ deficiencies were “extensive and serious.”
After the October ruling, Arguello asked defendants and plaintiffs to try to find a resolution outside of court, but they failed to do so.
The judge also criticized the Corps for failing to quantify how climate change will impact precipitation and, therefore, how that change could impact the need for more water storage. It’s unclear whether it’s practical and reasonable to build a reservoir to store Colorado River water that may not exist or be available, she previously said.
Denver Water argued that delaying or halting construction would be expensive and dangerous, but Arguello was not persuaded. She also criticized Denver Water for starting construction on the dam while the project’s legality was being challenged. The water provider cannot then argue the project should continue simply because it is already underway, she said.
“The Court does not find Respondents’ and Intervenor’s arguments about alleged cost, delay and the alleged urgent need to address droughts persuasive because these alleged hardships are largely self-inflicted,” she wrote.
Denver Water has said the expanded reservoir would anchor Denver Water’s northern supply system and help protect the utility’s ability to deliver water if its much larger southern supply system is impacted by fire, mudslides or drought.
“Denver Water has an enormous sense of urgency surrounding the project, considering increasingly variable weather and water supply patterns, how close we have come to falling short of water on the north side of our system in years past, our harrowing experiences with the threats and impacts of wildfire in our collection area and the need for system flexibility to ensure we can provide a critical public resource under crisis conditions,” the utility said in its statement Friday.
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