A US federal appeals court has ruled in favour of Denver Water in a dispute over the permit for its Gross Reservoir Expansion Project in Colorado, clearing a legal obstacle to filling the reservoir once the remaining work is complete.
In a decision issued on 15 September, the Tenth Circuit Court of Appeals reversed a district court ruling that had found fault with the US Army Corps of Engineers’ review of the project and barred Denver Water from diverting water into the expanded reservoir. The appeals court found that the Corps’ assessment of the project’s purpose, costs and the effects of climate change was reasonable and supported by the record.
The project involves raising Gross Dam by approximately 131ft (40m) and increasing the reservoir’s capacity from 42,000 acre-feet to around 120,000 acre-feet. Denver Water says the additional storage will give it greater flexibility in managing supplies for its service area. The Corps issued the permit at the centre of the dispute in 2017, following a review that began in 2003.
Roller compacted concrete placement for the dam raise was completed in June 2026, according to Denver Water. The utility expects further work on the dam to continue into summer 2027, with preparation of the expanded reservoir area continuing into 2028. It says filling could begin as early as 2028, depending on snowpack and water availability.
“We’re going to finish strong and look forward to putting an expanded Gross Reservoir to work for our customers and for the environment,” said Jeff Martin, Denver Water’s programme manager for the expansion.
