@USACE releases Draft EIS for Halligan Reservoir expansion

Reservoirs NW of Fort Collins

Click here to read the draft EIS. Here’s the abstract:

The Halligan Water Supply Project (Halligan Project) Draft Environmental Impact Statement (Draft EIS) evaluates the effects of enlarging the existing Halligan Reservoir located about 25 miles northwest of Fort Collins on the North Fork of the Cache la Poudre River (North Fork) in Larimer County in north central Colorado. The City of Fort Collins Utilities (Fort Collins) proposes to raise Halligan Dam by 25.4 feet to enlarge Halligan Reservoir from its current capacity of 6,400 acre-feet to approximately 14,525 acre-feet to provide about 7,900 acre-feet of additional annual firm yield to meet Fort Collins’ projected 2065 municipal and industrial water demands. The existing reservoir surface area is approximately 253 acres; the proposed enlargement would result in a surface area of approximately 386 acres. The Halligan Project would result in the placement of fill material into waters of the U.S., which requires a Department of the Army permit under Section 404 of the Clean Water Act

Halligan Reservoir aerial credit: City of Fort Collins

Halligan Dam is a concrete arch dam built over 100 years ago and will require rehabilitation in the near future to address safety risks. These safety risks would be addressed by Fort Collins under their proposed action during enlargement of the dam. Under the Project Alternatives, ownership of and responsibility for the dam rehabilitation would revert back to the North Poudre Irrigation Company. Under Fort Collins’ proposed action, Halligan Reservoir would continue to be filled with direct flows from the North Fork. Releases would be made to the North Fork downstream of the dam and would flow through Seaman Reservoir to the confluence with the Cache La Poudre River. From there, water would be exchanged up to Fort Collins’ intake or to the Monroe Canal intake and delivered to Fort Collins’ water treatment facility through the Pleasant Valley Pipeline. Under the proposed action, Fort Collins would maintain a minimum flow of five cubic feet per second in the North Fork from May 1 to September 30, a minimum flow of three cubic feet per second the remainder of the year, and forego all diversions to the enlarged pool and Halligan Reservoir for the three days that coincide with the forecasted peak runoff flow event for the North Fork.

This Draft EIS also evaluates the effects of the following alternatives to the Halligan Project: the No- Action Alternative; the Expanded Glade Alternative; the Gravel Pits Alternative; the Agricultural Reservoirs Alternative and the No-Action Alternative.

Reviewers should provide the Corps with their comments during the Draft EIS review period. The Corps will respond to substantive comments on the Draft EIS in a Final EIS. The Draft EIS and supporting documents are available at: or https://go.usa.gov/xEfp5 or http://www.nwo.usace.army.mil/Missions/Regulatory-Program/Colorado/EIS-Halligan/

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