Colorado: Not much love for proposed new water diversions

EPA raises questions about compliance with Clean Water Act

Denver Water plans to increase transmountain diversions through the Moffat collection system will be up for comment at a pair of upcoming meetings.
Denver Water plans to increase transmountain diversions through the Moffat collection system is not drawing rave reviews, as numerous entities have expressed significant concerns about impacts to water quality. bberwyn photo.

By Bob Berwyn

FRISCO — For all the detailed information in the 16,000-page study for Denver Water’s proposed new water diversions from the Western Slope, there are still more questions than answers, according to formal comment letters filed in the past few weeks.

As currently configured, the proposal to shunt more water from Colorado River headwaters streams to the Front Range could worsen water water quality in many streams that are already feeling the pain of low flows, EPA water experts wrote in a June 9 letter.

The letters came in response to release of a final environmental study by the U.S. Army Corps of Engineers, which is deciding whether to issue a permit for the project. The agency also took some heat for denying numerous requests to extend the comment period. Requests came from the U.S. Forest Service, Boulder County and even U.S. Sen. Michael Bennet.

In its June 9 letter, the EPA reiterated concerns that the study doesn’t adequately assess the downstream impacts of the diversions in the Fraser River, including in the Colorado River. In all, 36 streams would be affected by the new diversions. In some cases, the diversions could worsen water quality in streams already tainted by metals and other pollution. Unless adequately mitigated, those impacts could violate the Clean Water Act, the EPA wrote. The detailed EPA comments are online here.

In some cases, the Corps study doesn’t even address all the waters where impacts are happening, the EPA said, pointing out threats to Grand, Granby and Shadow lakes in Grand County from additional nutrient loading.

The EPA acknowledged two other partly overlapping agreements that may address some — but probably not all — of the lingering concerns over stream depletion consequences for the entire web of aquatic stream life, from tiny water bugs to native cutthroat trout.

The final Environmental Impact Statement doesn’t include enough detail to determine whether all the proposed mitigation will be effective, assistant regional EPA administrator Martin Hestmark wrote. It’s up to the Corps to piece together a permitting process that meets all applicable Clean Water Act standards. The EPA recommends adding an adaptive management plan, with assurances of long-term monitoring, as a permit condition, with enforceable thresholds and triggers and specific commitments to mitigation actions.

Boulder County also isn’t satisfied that the voluminous document has addressed key concerns, and the U.S. Forest Service wants to make sure the project won’t degrade valuable public natural resources.

At issue is Denver Water’s proposal to develop another 18,000 acre of water from the West Slope, divert it through the Moffat Tunnel and store it in an enlarged Gross Reservoir in Boulder County. The Moffat Tunnel collection system expansion project would help Denver Water balance its water supplies in different parts of the system. Without the water, some Front Range communities are vulnerable to supply disruptions during drought, the final study concluded, singling out Arvada, Westminster and the North Table Mountain Water and Sanitation District.

Denver Water has identified a supply shortfall of about 34,000 acre feet for the 2016-2050 time frame. Upping diversions and increasing storage in Gross Reservoir by 77,000 acre feet would help fill the gap, with more water conservation measures planned to meet the rest of the shortfall.

According to the EPA’s letter, the Corps’ final environmental study shows that many of the stream reaches affected by existing and proposed new diversions may have already crossed ecological tipping points, which supports the EPA’s concern that new diversions could contribute to “significant degradation” in the Fraser River, the Williams Fork River and the Upper Colorado.

Specifically, the EPA addressed nutrient loading and metals pollution. Some streams affected by the proposed project are exceeding or approaching thresholds association with aquatic impacts.Similarly, new diversions from the Fraser River could lead to increased concentrations of metals deemed harmful to aquatic life. Worsening water quality in streams that are already affected by pollution is a big non-no under the Clean Water Act.

The EPA letter also called the Corps to task for describing impacts to the Colorado River as minor.”We are concerned that impacts to the stream ecosystems of the West Slope may be more substantial than outlined and characterized in the final EIS,” the EPA wrote.


2 thoughts on “Colorado: Not much love for proposed new water diversions

  1. Until the massive influx of people to Colorado stops, diversions like this will continue to increase. No one wants to discuss the actual cause of the problem.

  2. It’s easy. Tell Denver and the rest of the Front Range to start recycling their wastewater, retreating it into potable water. Problem solved, and it’s probably much less expensive than diverting yet more water out of the Upper Colorado River Basin and other places from the Western Slope. We’re tired of having our streams diverted to support the Front Range’s unrealistic population growth. Much love, Denver, but enough is enough.

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