Federal appeals court clears way for $600 million Gross Dam project’s completion, tell me about this news in (https://www.denverpost.com/2026/09/15/ruling-gross-reservoir-dam-denver-water/)

A three-judge panel of the U.S. Court of Appeals for the 10th Circuit ruled in favor of Denver Water, clearing the path for the completion and filling of the Gross Reservoir Expansion Project in Boulder County, Colorado.Key Details of the Ruling

• Court Decision: In a unanimous 3–0 opinion authored by Judge Timothy M. Tymkovich, the 10th Circuit vacated a lower court injunction that had blocked Denver Water from taking the final steps to make use of the expanded reservoir.
• The Legal Dispute: Six environmental groups, led by Save the Colorado, challenged the project under the Clean Water Act and the National Environmental Policy Act (NEPA). In 2024 and 2025, U.S. District Senior Judge Christine Arguello had ruled that the U.S. Army Corps of Engineers improperly issued a dredge-and-fill permit in 2017 by improperly defining the project’s purpose and failing to fully consider alternatives that avoided wetlands. While she permitted dam structural work to proceed for safety reasons, she barred Denver Water from tree clearing and filling the enlarged reservoir.
• The Appeals Court’s Finding: The 10th Circuit rejected the lower court’s reasoning, finding that the Army Corps of Engineers acted reasonably and within the law. The court held that the Corps was entitled to evaluate the project’s dual goalssupplying more water to meet demand and rebalancing water delivery between Denver Water’s northern and southern systemsand that the Corps’ assessments regarding cost and climate change were well-supported by the administrative record.

The Scope of the Project

• Scale & Cost: The roughly $600 million expansion raises the existing Gross Dam by 131 feet (reaching a final height of 471 feet), making it the tallest dam in Colorado.
• Capacity: The project nearly triples the reservoir’s storage capacity, allowing Denver Water to store an additional 18,000 acre-feet of water annually (around 5.8 billion gallons) to serve approximately 1.5 million customers (about 25% of Colorado’s population).

Reactions to the Decision

• Denver Water: The utility welcomed the ruling, stating that the expansion is critical for long-term water security, system redundancy, and flexibility amid severe drought, extreme weather, and wildfire risks.
• Environmental Groups: Conservation advocates expressed strong disappointment, arguing that diverting more water will further strain the fragile Colorado River basin and cause lasting ecological damage to local forests and streams.