The Tenth Circuit Court of Appeals has reversed a lower court ruling that halted a major water project by Denver Water. The decision, issued on September 15, 2026, affects not only Denver Water but also environmental groups and local communities concerned about water resources and environmental impacts. The ruling allows Denver Water to proceed with filling the expanded Gross Reservoir, a project that has been in development for over two decades.

The case, Save The Colorado v. Graham (Docket No. 25-1137), centers on the Moffat System Collection Project, which aims to increase the water supply for Denver and surrounding areas. The project faced opposition from environmental groups, which argued that the U.S. Army Corps of Engineers (the Corps) violated environmental laws during its permitting process.

Background

Denver Water, a municipal utility, proposed the Moffat System Collection Project in response to predictions of a looming water shortage. The project involves raising the Gross Dam by 131 feet to increase the reservoir's capacity by an additional 77,000 acre-feet of water. To proceed, Denver Water needed a wetlands permit from the Corps, which it received in 2017 after a lengthy review process.

However, environmental groups, including Save The Colorado, challenged the Corps's decision, claiming it failed to comply with the Clean Water Act (CWA) and the National Environmental Policy Act (NEPA). They argued that the Corps did not adequately consider the project's environmental impacts and alternatives during its permitting process. The groups sought to have the permit vacated and the project halted.

The Ruling

The Tenth Circuit Court found that the lower court had erred in its assessment of the Corps's actions. The district court had ruled that the Corps violated the CWA and NEPA by narrowly defining the project's purpose and failing to consider the costs and climate change impacts adequately. However, the appellate court disagreed, stating, "The Corps may include a project’s multiple related purposes when defining the project’s purpose." Furthermore, the court noted that the Corps's determinations regarding costs and climate change were reasonable and supported by the record.

Chief Judge Timothy Tymkovich, along with the other circuit judges, emphasized that the Corps exercised its discretion appropriately in evaluating the project. The court's reversal allows Denver Water to proceed with filling the Gross Reservoir, which had already undergone significant construction.

Impact

This ruling has significant implications for water management and environmental law in the region. It sets a precedent for how federal agencies can define project purposes and consider environmental impacts when issuing permits. The decision may influence future projects that require federal approval, particularly those affecting water resources and ecosystems.

Local communities and stakeholders are likely to feel the effects of this ruling as Denver Water moves forward with its plans. The project is expected to enhance water supply reliability for Denver and surrounding areas, addressing concerns about water shortages. However, environmental groups remain vigilant and may seek other avenues to address their concerns about the project's impact on local ecosystems.

What's Next

While the Tenth Circuit's decision is a significant victory for Denver Water, the environmental groups involved in the case may consider further legal options. They could seek to appeal the ruling or explore other legal avenues to ensure environmental protections are upheld. Details were not available in the court filing regarding any pending related cases.