Gross Reservoir expansion makes sense — Boulder Daily Camera

The dam that forms Gross Reservoir. Photo: Brent Gardner-Smith/Aspen Journalism

From the editorial board (Quentin Young) of the Boulder Daily Camera:

Denver Water serves 1.4 million people in Denver and surrounding communities, and that figure will rise substantially in the coming decades. As more residents demand service, climate change increasingly will exert its own strain on the water supply. One of the primary ways the utility plans to meet this imminent challenge is by expanding one of its northern storage facilities, Gross Reservoir, in the foothills southwest of the city of Boulder.

The project has met with intractable opposition. It’s the subject of lawsuits and uncertain government reviews. Neighbors are scandalized by the prospect of years of disruptive construction, and some environmentalists contend the project won’t even be able to perform its intended purpose.

But a dispassionate consideration of the project leads to the conclusion that Denver Water’s plan to expand Gross Reservoir is a reasonable and responsible measure, provided the utility proceeds with the utmost sensitivity to the residents who would be impacted by construction and with the expectation that increased storage is no substitute for continued conservation efforts.

The roots of the project go back to the proposed Two Forks Dam. Denver Water had proposed storing water from the Colorado and Platte rivers by building a 615-foot dam southwest of Denver near Deckers. But a coalition of environmental groups successfully opposed the project, which the Environmental Protection Agency spiked in 1990. Environmentalists argued at the time that a better option would be for Denver Water to expand a storage facility it already operated: Gross Reservoir.

Gross Dam enlargement concept graphic via Denver Water

Now that the utility is following opponents’ former advice, environmentalists have changed their mind about Gross. The project would raise Gross Dam by 131 feet to 471 feet, roughly tripling the reservoir’s current capacity of 41,811 acre-feet (for comparison, Denver Water’s largest reservoir, Dillon, has a capacity of more than 257,000 acre-feet). Critics say the expansion would result in the state’s tallest dam, and much of the opposition focuses on the project’s substantial environmental impact. It would require years’ worth of noisy construction, traffic and the removal of about 650,000 trees. The reservoir pulls water from the headwaters of the Colorado River, and critics argue that the utility should refrain from further depleting that waterway, which runs all the way to the Gulf of California and is subject to the Colorado River Compact, an agreement that governs water allocation in seven states that rely on the river as an invaluable resource. Population growth in the Southwest has stressed the river, and climate change is expected to further compromise the river’s capacity to deliver water to users. Some Gross expansion opponents even assert that there won’t be enough water available from the Colorado River Basin to fill a bigger reservoir. And anyway, the opponents say, water needs can be met through conservation rather than dam-building.

Construction to expand Gross Reservoir would indeed bring acute hardship to nearby residents, and concern for local environmental damage should not be dismissed. But construction is temporary, and the environmental impact seems less intolerable than merely regrettable when weighed against the project’s purpose of ensuring for decades the delivery of a vital resource to thousands of people.

Utilities should be judicious in exercising their rights to Colorado River Basin water, but the volume associated with the proposed Gross expansion is relatively small. The entire Denver Water utility accounts for less than 2% of the state’s total water use, while it serves about 25% of the population. As part of planning for the expansion, Denver Water worked with West Slope communities in the Colorado River Basin to earn support for the project, efforts that in 2012 resulted in the Colorado River Cooperative Agreement. The CRCA, which depends on final approval of the Gross Reservoir expansion, calls for Denver Water to help restore habitats and maintain flows in the Fraser River, a Colorado River tributary in Grand County. Some West Slope officials so favor implementation of the CRCA that a Grand County commissioner in March warned of “a ton of litigation” were Boulder to block the Gross expansion.

Colorado River flows will almost certainly decrease due to climate change in future decades. A widely cited 2017 study suggests the river increasingly will be subject to droughts, and flows could drop more than 35% by the end of the century because of higher temperatures. But this doesn’t necessarily constitute an argument against expanding Gross. No one can claim with certainty that flows would drop such to render useless an expanded reservoir, but Denver Water would certainly be justified in viewing the threat of persistent droughts and lower flows as a reason to increase storage capacity, since there’s more incentive to collect water during the fewer occasions it’s available. The utility would be seen to have failed customers were it to find itself with nowhere to store precious water to which it had rights.

That Denver Water should do more to promote conservation gets no argument here. The utility’s customers have already demonstrated that they can get by splendidly with reduced volume — they’re using about 20 percent less water today than 15 years ago, according to Denver Water CEO Jim Lochhead — and there’s much room for further conservation. But conservation has limits, and Denver Water says it won’t be able to meet future demand solely by this method. In Denver alone, the current population of 729,000 is expected to swell by more than 20% in just 20 years. Besides, the project is meant not just to add yield to the utility’s system but also stability. The vast majority of Denver Water’s storage is in the south part of its system, and forest fires near those facilities, such as the Buffalo Creek Wildfire in 1996, have exposed a vulnerability that an expanded Gross would address.

The proposed expansion of Gross Reservoir has provoked waves of protest from Boulder County residents, and the county has asserted what it claims is its right to review the project. Known as a 1041 process, the move is contested by Denver Water. But though Denver Water doesn’t serve Boulder-area residents, water users throughout Boulder County every day enjoy the use of water pulled from the Colorado River, and water customers in such Boulder County communities as Longmont, Louisville, Lafayette, Erie and Superior are participants in the proposed Windy Gap Firming Project, which involves the construction of a whole new reservoir, not just an expansion, west of Carter Lake to store water from the Colorado River Basin. (That project similarly is tied up in litigation.)

Denver Water has already secured the bulk of required regulatory approvals for the expansion of Gross Reservoir. A final decision from the Federal Energy Regulatory Commission, whose staff has already recommended approval, is pending. Denver Water needs the FERC approval, because Gross also serves as a hydroelectric facility. Roadblocks include a lawsuit brought by a coalition of environmental groups that is led by Save the Colorado and Boulder County’s 1041 review.

Boulder County officials have a legitimate interest in reviewing what would be the largest construction project in county history, and they are encouraged to take an exhaustive look at Denver Water’s plans. Any objections to the expansion of Gross Reservoir, however, should be based on factors intrinsic to the proposal, not on a mere preference for Gross to be left alone.

Quentin Young, for the editorial board, quentin@dailycamera.com, @qpyoungnews

Denver Water’s collection system via the USACE EIS

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