Tenth Circuit lifts injunction blocking Denver Water’s Gross Reservoir expansion

The U.S. Court of Appeals for the Tenth Circuit has lifted an injunction blocking Denver Water’s Gross Reservoir expansion, allowing the utility to continue construction and eventually fill the expanded reservoir.

In a published opinion filed Sept. 15, the Tenth Circuit’s ruling reversed the U.S. District Court for Colorado, vacated a permanent injunction and sent the case back with instructions to rule against the environmental groups that challenged the project. The panel concluded that the U.S. Army Corps of Engineers reasonably evaluated the project’s purposes, alternatives, costs and climate-change evidence.

The ruling leaves Denver Water’s Clean Water Act Section 404 permit in place for the issues challenged in the lawsuit. Denver Water said in a statement about the ruling that it can proceed with final construction, site preparation and eventual filling of the expanded reservoir.

Arvada City Manager Wick told the City Council on Sept. 15 that the ruling meant “the project will be able to move forward from this point,” according to the meeting recording. Wick said city staff would review the opinion and work with Denver Water as the project advances.

The ruling does not create a new construction deadline. Denver Water said in a July project update that the roller-compacted-concrete portion of the dam topped out June 3, with work still remaining on the final foot of concrete, a water gate, the spillway crest, a spillway bridge and a stilling basin. The utility estimated that about 1.5 years of dam-construction work remained at that time.

The project is designed to raise the dam 131 feet and increase storage from about 42,000 acre-feet to 119,000 acre-feet. Denver Water says the additional roughly 77,000 acre-feet of storage will give it more flexibility during drought and help serve its approximately 1.5 million customers.

Denver Water’s tree-removal plan amendment describes about 415 acres of planned forest clearing, including roughly 270 acres on National Forest System land. It also outlines truck traffic on Gross Dam Road, helicopter logging, dust and noise controls, wildlife restrictions, and wetland and stream-restoration measures affecting Boulder, Jefferson and Gilpin counties.

Environmental groups have argued that the expansion would put additional pressure on an already stressed Colorado River system. The court’s decision addressed whether federal regulators adequately evaluated the project, not whether all of its projected effects have occurred.