Water dispute: Proposed Gross Reservoir expansion pits Boulder County Commissioners, others against Denver Water

It’s hard to imagine a local issue much more contentious than the proposed expansion of Gross Reservoir, one that was not resolved as of this writing.

The largest construction project ever in Boulder County would destroy between 200,000 and 650,000 trees. Opponents urge a greater focus on water conservation instead.

“(The dam expansion) is going to be ... happening in a county that cares deeply about its environmental footprint,” said Jennie Curtis, executive director of the Garfield Foundation, an environmental nonprofit.

That footprint would be substantial. The proposal to raise the dam by 131 feet would more than double reservoir capacity, also more than doubling the amount of concrete in the complete dam to nearly 1.5 million cubic yards.

Curtis also pointed out that the data used in Denver Water’s environmental impact statement dates to 2002, predating concerns about climate change.

Denver Water said it needs to bolster water supplies for its customers north of Denver. With the exception of several thousand acre feet to increase the flow of Boulder Creek when it runs low, very few Boulder County residents would receive water from the project.

Boulder resident Dan Johnson, who has done engineering work for Denver Water, said the impact is lower than if the project were started on a new site. He added that Denver Water plans to mitigate the impact on local residents as much as possible, having workers park offsite, for example.

“The problem is that nature didn’t put water where people want to live,” he said, adding that when the current dam was built in 1954, planning included expansion for future needs.

Municipalities in Boulder County currently use less than half the gallons per capita they used in 2000, and other Boulder County municipalities have also made significant improvements in water conservation.

Among the communities of Boulder County, Pinebrook had the lowest daily residential per capita use at 55 gallons, while Erie had the highest at 93 gallons. Boulder residents used 72 gallons per capita in 2018 compared with 165 gallons in 2000.

Overall use among Denver Water customers has continued to fall even as the population continues to rise significantly, just as it has in Boulder County.

Curtis and other environmental advocates say more conservation should be implemented before considering expansion. Denver Water argues it must increase water storage now to assure future supply.

In addition to several environmental groups that oppose the dam expansion, Denver Water tangled with the Boulder County Board of Commissioners, which unanimously voted to uphold the land use director’s ruling to require review by the county. Denver Water sued the county, while still taking initial steps in the review process.

Save the Colorado, an environmental group that seeks to preserve the Colorado River, from which some of Denver’s water flows, also was allowed to join the county’s suit in Boulder District Court against Denver Water. It and five other environmental advocacy groups had originally filed suit against Denver Water in December 2018.

Denver Water planned to begin expanding Gross Reservoir in 2019. It was unclear whether a compromise was possible.“It could be months. It could be years,” Curtis said.

by Cindy Sutter