Court Cleared Denver Water Reservoir Expansion Project
The 10th Circuit Court of Appeals ruled that the permit for the Gross Reservoir expansion complies with federal law.
Updated on Sept. 22, 2026 in Utilities
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The 10th Circuit Court of Appeals has upheld the U.S. Army Corps of Engineers permit for the Gross Reservoir Expansion Project. This ruling allows Denver Water to proceed with major construction and future water storage efforts.
Why it matters
The expansion is designed to provide critical drought protection and greater operational flexibility for managing water supplies against risks like wildfires and climate shifts. It serves a population of 1.5 million people within the Denver Water service area.
The project will increase storage from 42,000 to 120,000 acre-feet, representing an 11% increase in total supply capacity for 1.5 million customers. Denver Water has committed $30 million toward 60 distinct environmental offset projects.
The players
Denver Water
This public agency serves as the primary provider of water for 1.5 million residents and businesses in the Denver area.
U.S. Army Corps of Engineers
This federal agency is responsible for overseeing the permitting process for large-scale water infrastructure projects.
10th Circuit Court of Appeals
This federal court holds jurisdiction over cases originating from districts including Colorado, Wyoming, and Utah.
The details
The construction plan involves adding material to the top and bottom of the dam and performing underwater work on the upstream side. To prepare the site for the larger footprint, crews will undertake extensive tree removal within the expansion zone.
Timeline
Denver Water began the initial permitting process for the expansion in 2003.
The 10th Circuit Court of Appeals issued its final ruling on September 15, 2026.
Major dam construction activities are scheduled to finish by the summer of 2027.
Reservoir filling operations could begin as early as 2028.
Market Landscape
This judicial approval represents a milestone in Western water management by validating infrastructure development under stringent federal environmental law standards. It positions Denver Water to secure long-term utility reliability compared to regional competitors relying on aging supply systems.
The expansion will eventually increase the overall reliability of the water supply for all 1.5 million residents in the Denver Water service area. Residents should not expect immediate changes to their monthly bills or water usage, as the project focus remains on long-term infrastructure.
The takeaway
The court decision provides a stable path forward for significant regional water storage upgrades. Residents can anticipate continued construction activity in the Boulder County area over the next few years as the project matures.
Further reading
Learn more about local infrastructure projects in the Utilities section.
Live Poll
Do you believe expanding reservoir capacity is the best approach to ensure water security in your area?
