The future of Denver Water’s $531-million project to raise the height of Gross Dam by 131 ft may be in question after a federal judge in Colorado found the U.S. Army Corps of Engineers violated the Clean Water Act and National Environmental Policy Act when it issued a dredge-and-fill permit for the work. But the judge deferred on a final ruling and is allowing construction to continue ahead of a planned pause for the winter.

Denver Water is raising the dam from 340 ft to 471 ft to nearly triple the capacity of Gross Reservoir from 42,000 acre-ft of water to 119,000 acre-ft. Officials of the city-owned utility say the project is needed to improve the system’s ability to meet growing demand and withstand drought, as well as to address an imbalance between the water utiliry's south system, which delivers 80% of its supply, and its north system, which includes the reservoir.