US permit for Colorado reservoir violates environmental laws, judge rules

By Michael Doyle | 10/18/2024 01:22 PM EDT

With a 2017 federal permit, Denver Water began work in 2022 expanding the Gross Dam and Reservoir to serve a population of more than 1.5 million.

Construction equipment on top of a dam on a river.

Following nearly 20 years of permitting and planning, Denver Water began construction to expand the Gross Dam in 2022. Denver Water

Environmentalists challenging what could become Colorado’s tallest dam prevailed this week as a federal judge ruled the Army Corps of Engineers erred with its issuing of a key permit required for the Gross Dam and Reservoir project.

In a sharply worded — but not fatal — blow to the project intended to triple the size of the existing Gross Reservoir, U.S. District Judge Christine Arguello found that the Army Corps’ permit violated both the Clean Water Act and the National Environmental Policy Act. Now, environmental groups, the Army Corps and Denver Water will have to figure out a remedy.

“The debate over the Gross Dam and Reservoir expansion proposal is both public and passionate,” Arguello wrote in her 86-page opinion issued Wednesday.

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The ambitious project includes enlarging the existing Gross Dam by 125 vertical feet and inundating approximately 400 acres of mostly forested land, which Arguello noted would “require the excavation of 1.6 million tons of rock and destroy more than 500,000 trees.” The project requires a permit from the Army Corps of Engineers because it involves discharging fill material into wetlands.

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