Gross Reservoir Expansion

Denver Water’s Gross Reservoir expansion raises Gross Dam in Boulder County, Colorado, to increase water storage for the utility’s supply system.

The project relies on Colorado River basin water rights, including water conveyed through the Moffat Tunnel. Its permitting and environmental review were challenged by opponents who questioned the analysis of climate change, drought, alternatives, and downstream effects; the Tenth Circuit upheld the federal permits, allowing construction completion and reservoir filling. The project brings together water-supply planning, environmental review, and the effects of major infrastructure on rivers and communities.