Boulder County’s Gross Reservoir Can Proceed With Expansion Following Lawsuit

Federal officials have given the go-ahead to expand Gross Reservoir in Boulder County. 

That means Denver Water has overcome a huge hurdle in its effort to increase storage capacity. Gross Reservoir provides water to 1.5 million Front Range customers. 

“Expanding Gross Reservoir is a critical project to ensure a secure water supply for nearly a quarter of the state’s population,” Denver Water CEO Jim Lochhead said in a statement. “The project provides the system balance, additional storage and resiliency needed for our existing customers as well as a growing population.”

In 2018, some environmental groups sued three U.S. government agencies in an effort to stop the expansion. They argued that it would harm aquatic life and wildlife as well as hinder streamflows, adding that the Colorado River needs to be better protected.

On Friday, the Federal Energy Regulatory Commission ordered Denver Water to proceed with the project, which will raise the height of the reservoir’s existing dam by 131 feet. That will increase the reservoir’s capacity by 77,000 acre-feet, according to the plan.

Lochhead has said that Denver Water will only take extra water from tributaries during wet years, avoiding periods of drought.

It’s been a long road for the utility, which began the permitting process for the expansion seventeen years ago. Denver Water plans to finish the design next year, followed by four years of construction.