Moffat Collection System Project

Additional extension to comment period

Denver Water and the U.S. Army Corps of Engineers (Corps) were asked by several local agencies, individuals and stakeholder groups to consider an extension of the public comment period for Denver Water’s Draft FERC Hydropower License Amendment Application and the Corps’ Draft EIS and pending Section 404 permit application for the Moffat Collection System Project.

Denver Water’s Moffat Supply Project proposes to enlarge Gross Reservoir to help resolve three major supply challenges: a future water shortfall (supply), the risk of running out of water in a future drought (reliability) and a serious imbalance in Denver Water’s collection system (vulnerability).

Why Enlarge Gross Reservoir?

Supply: Denver Water has identified a shortfall in supply beginning in 2016 and growing to 34,000 acre-feet per year by 2030. Approximately 16,000 acre-feet of the shortfall is expected to be addressed through additional conservation, leaving Denver Water with an annual shortage of 18,000
acre-feet (one acre-foot is equal to 325,851 gallons of water and will supply more than two single-family households for a year).

Reliability: During the 2002 drought, Denver Water came perilously close to running out of water in the Moffat Collection System. Without water in the Moffat system, Denver Water would lose the operation of one of its three treatment plants and have difficulty meeting the needs of its customers and raw water commitments to Arvada, Westminster, Consolidated Mutual and others.

Vulnerability: Denver Water’s system is out of balance. Approximately 80 percent of its water supply relies on the unimpeded operation of Strontia Springs Reservoir. Emergencies above this reservoir threaten the operation of the entire system, as the Hayman and Buffalo Creek fires highlighted in recent years.

The project

If approved, the project would produce 18,000 acre-feet of new supply by expanding an existing reservoir rather than building a new one. The current dam height would increase from 340 feet to approximately 465 feet. The proposed project would increase Gross Reservoir from its current storage capacity of 41,811 acre-feet to approximately 114,000 acre-feet – an increase of 72,000 acre-feet. (Denver Water has determined four acre-feet of storage are needed for every one acre-foot of supply.)

Because Gross Reservoir was originally designed to be this larger size, other facilities, such as the Moffat Tunnel and South Boulder Canal, do not need to be modified and no additional water rights are needed. The additional water would be carried through the existing Moffat Tunnel from the Fraser River basin and Williams Fork River basin in Grand County, as well as from South Boulder Creek basin. Streamflow in the Fraser and Williams Fork rivers and South Boulder Creek would only be decreased by this project during wet and average years during the runoff months.

Denver Water believes enlarging Gross Reservoir would deliver the most benefits at the least cost and with similar environmental impacts compared with the other practicable alternatives. 

The U.S. Army Corps of Engineers is now preparing an Environmental Impact Statement to study the impacts of each proposed project alternative.

As stated in the National Environmental Policy Act, there are four main steps the Corps must follow to complete the Environmental Impact Statement:

1. Public consultation (completed November 2003)
2. Preparation of Moffat Collection System Project scoping summary report (PDF) (completed February 2004. Note: The full report is available for review at Denver Water during business hours, 8 a.m. to 4 p.m., Monday through Friday, except for holidays. Call 303-628-6414 for more information).
3. Draft Environmental Impact Statement (expected to be released summer 2009)
4. Final Environmental Impact Statement and Record of Decision

Questions?

Denver Water and the U.S. Army Corps of Engineers know it’s important that interested and impacted parties know of this study and the public process/meetings. The Corps is the lead agency responsible for the study and analysis. If you have suggestions and/or concerns, direct your comments to the Corps once the Draft Environmental Impact Statement is released.

Denver Water also is interested in your comments and will answer what questions it can at this time. Send questions to publicinformation@denverwater.org . Denver Water will provide more information on the process on its Web site as it becomes available; however, once the Draft Environmental Impact Statement is released, all official correspondence must go through the Corps.

Questions regarding the proposed project, public consultation process, scoping document and Environmental Impact Statement process can be directed to:

To be kept informed on the Moffat Collection System Project, send us your e-mail address.

Scope of Work Phases