Denver Water is planning a major expansion of the reservoir that will increase height of the Gross Reservoir Dam outside Boulder by 131 feet and water storage by 77,000 acre-feet. Local residents and environmental groups are fighting against the expansion. (Chris Schneider, Special to The Colorado Sun)

Denver Water sued Boulder County in federal court Tuesday saying county officials are slow-walking decisions on plans to expand Gross Reservoir, threatening crucial federal permits and construction timelines. 

Denver is essentially telling Boulder County to hurry up and say “no” to the raising of the existing dam and water pool, noting that two of the county’s three commissioners have already publicly stated their opposition to, and desire to stop, the expansion project.

“Boulder County is endangering the project through delays, repeated and expanding requests for information — information demands that duplicate the already completed federal permitting process in which Boulder County participated,” Denver Water said in a release accompanying the filing in U.S. District Court.

Denver said it faces “potential for months of additional hearings.” 

Repeated requests for more information from Denver that the water agency believes it has already provided are “setting the project up for failure and rendering further involvement with the 1041 process futile.”

A “1041” county construction permit is one of the last things dam builders need before proceeding with moving dirt, and often come only after decades of meticulous planning and battling lawsuits

“The actions of a single local jurisdiction, Boulder County, threaten to derail and undermine a federally permitted and state supported project vital to a safe and secure water supply for one-quarter of Colorado’s population,” the Denver Water release said.

The proposed $464 million project would raise the dam by 131 feet and water storage by 77,000 acre-feet. Construction would impact surrounding forests, roads and neighbors.

Denver collects Western Slope water in the reservoir and sends supply down Boulder Creek to be treated for use by Front Range communities. The dam was built by Denver in the 1950s. 

Boulder County attorneys did not respond to requests for comment Tuesday.

Michael Booth is the Sun’s environment writer, and co-author of the Sun’s weekly climate and health newsletter The Temperature. He is co-author with Jennifer Brown of the Colorado Book Award-winning food safety investigation “Eating Dangerously.” Booth was part of teams that won two Pulitzer Prizes for breaking news. He also writes frequently about inexplicable obsessions that include tamarisk, black-footed ferrets and tire fires. Booth also serves as the underpaid driver for four children, and plans to eventually hike every inch of Colorado.