Judge allows Denver Water two more weeks of Gross Dam construction before court-ordered halt

The state’s largest water utility will have two weeks to complete any necessary work on its $531 million dam expansion project before a court-ordered construction halt takes effect, a federal judge ruled Sunday.

The granting of a temporary window for construction follows an order late Thursday by U.S. District Court Judge Christine Arguello blocking Denver Water’s expansion of Gross Reservoir outside Nederland and barring further construction work to raise the height of the dam. The U.S. Army Corps of Engineers violated federal environmental law during the permitting process and must redo major permits, the judge ruled, siding with environmentalists who sued over the project.

In response to the order, Denver Water asked the judge to allow dam construction to continue while the utility appealed her decision.

“Denver Water faces enormous irreparable harm from the order stopping ongoing project construction, which may threaten the safety of the half-constructed dam; require Denver Water to quickly lay off hundreds of construction workers; impose millions in additional materials and equipment costs on Denver Water and its ratepayers; and increase the risk of water shortages,” lawyers for the utility wrote in their request.

Arguello denied the utility’s request to allow construction to continue during the appeal but granted the 14-day stay on her order blocking all construction. After a yet-to-be-scheduled hearing, she will decide exactly how much more construction to allow to make the existing dam structurally sound.

Denver Water — which provides water for 1.5 million people in the metro — is legally required by the Federal Energy Regulatory Commission to finish the Gross Reservoir expansion project in 2027 because the dam is also a hydroelectric facility. I

f construction is delayed, the utility will not be able to meet that deadline, exposing it to financial penalties, the loss of its hydropower license or criminal prosecution, Denver Water’s attorneys wrote.

Denver Water planned to raise the dam’s height by 131 feet to 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.

Construction on the dam was slated to begin again for the spring season this week, according to the utility. The dam currently rises to 60% of its planned final height but has no spillway and other critical infrastructure needed to help it respond to flooding.