Federal Court Ruling Clears Way For Completion Of Gross Reservoir Expansion Project
10th Circuit Court of Appeals finds key federal permit was issued lawfully.
By Todd Hartman
The Gross Reservoir Expansion Project, more than 20 years in the planning, permitting, and construction process, is now on a straightaway to the finish line.
That’s after a Sept. 15 decision from the 10th Circuit Court of Appeals that removed a long-lingering legal cloud over the project. The decision declared that a key permit from the U.S. Army Corps of Engineers was issued in accordance with federal environmental law.
The ruling, following several years of back-and-forth litigation at the federal district and circuit court levels, puts an end to the permitting dispute and allows Denver Water to proceed with final work at the site and, eventually, fill the expanded reservoir with additional water.
“Denver Water began the permitting process for Gross expansion in 2003 and has worked tirelessly over more than two decades to plan and construct an environmentally responsible project that protects habitats and streamflows on both sides of the Continental Divide,” the utility said in a statement marking the 10th Circuit Court ruling.
“An expanded Gross Reservoir is vital to the future of the Denver region, giving Denver Water far greater ability to flexibly manage constrained water supplies amid the growing risks of catastrophic wildfire and weather extremes that accompany the challenges of drought and climate change already upon us.”
The expansion will nearly triple the capacity of Gross Reservoir, from 42,000 acre-feet to about 120,000 acre-feet at its new size. Filling the additional storage space could begin as soon as 2028, but the timing and pace of filling will ultimately depend on snowpack levels and water availability.
Last week’s ruling won’t have any immediate impact on current water supply or drought relief for the 1.5 million people in Denver Water’s service area. But greater capacity at the reservoir in southwestern Boulder County will serve as significant drought protection in the years ahead.
The added storage capacity will bulk up Denver Water’s supplies by about 11% and add critical storage to the north side of the utility’s system, giving it far more flexibility to deliver water when and where it’s needed, including the opportunity to leave additional water in streams that feed the upper Colorado River when conditions require.
That’s one of many environmental benefits the expansion will provide.
Denver Water has made $30 million in commitments to more than 60 projects that offset various impacts of the expansion on land, water and wildlife. Those projects include stream restorations on the Williams Fork and Fraser rivers in Grand County and South Boulder Creek in Boulder County.
In fact, Denver Water completed and paid for many such projects before the Gross Reservoir Expansion Project had cleared all its regulatory and legal hurdles — as a show of good faith to communities on the Front Range and West Slope.
Workers at the expansion site will be busy for at least another two years.
Activities on the dam itself — detailed additions at both the very top and very bottom of the dam, as well as underwater work on the upstream side of the dam — should wrap up in the summer of 2027. Reservoir site preparation, including removal of trees in the expansion area, is expected to begin in 2027 and wrap up by 2028.
Improvements to recreation will kick off in 2028. That includes new areas to access the water for boating and restoration of areas disturbed for dam construction.
“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, the program manager for the expansion.
“We are grateful for the diverse team and our project partners who have worked on this project for over 20 years and who were always focused on executing it in the right way; we are excited to now see it through.”