Denver Water plans appeal of judge’s ban on filling expanded Gross Reservoir

Denver Water will appeal a federal judge’s order barring the utility from filling Gross Reservoir once the construction on the new, higher dam is complete.

The utility on Tuesday filed a notice to the 10th Circuit Court of Appeals stating it will challenge U.S. District Judge Christine Arguello’s recent order that prohibits the filling of the reservoir to take advantage of the higher capacity until federal permitting processes are redone. Arguello found that the U.S. Army Corps of Engineers violated federal environmental law during its permitting process when it analyzed the environmental impact of the $531 million reservoir expansion.

Construction on the dam — which is being raised by 131 feet– can continue while the appeal proceeds. Arguello on May 30 lifted her previous ban on the construction after finding it would be dangerous to halt the project. Work began in 2022 is about 60% complete.

The expanded reservoir would be triple the size of the current body of water outside Nederland and add enough water to serve about 156,000 more households.

Arguello on Thursday ordered the Corps of Engineers to redo its monthslong permitting process for the project.

Environmental groups opposed the reservoir expansion because it requires the clear-cutting of a half-million trees and will cause the utility to draw more water from the already-strained Colorado River system.

Federal regulators failed to properly analyze the project’s environmental impacts or analyze less harmful options for Denver Water to meet its water supply needs, the project’s opponents argued.

Arguello in October issued a ruling agreeing with some of the groups’ arguments and ordered the two sides to work out a solution. When a consensus could not be reached, she imposed her own orders.

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