PERMITTING

Wild Horse Reservoir Federal Permitting

For the proposed Wild Horse Reservoir Project, the Bureau of Land Management (BLM) is the lead federal agency for the National Environmental Policy Act (NEPA) process that will evaluate  environmental, cultural, and local community impacts. BLM will conduct this evaluation process and prepare a detailed report, called an Environmental Impact Statement (EIS). This report will evaluate and disclose the impacts of the proposed project – as well as alternatives – that have the potential to meet Aurora’s water needs to the year 2075.

In addition to the proposed Wild Horse Reservoir location, two additional alternative sites in Park County have been identified for further evaluation: a site just south of the proposed project and a possible expansion of Spinney Mountain Reservoir. All the alternatives have components in Park County, Colo. (See map of alternatives and descriptions below).

Project Alternatives

Map overview of Wild Horse Reservoir project alternatives, showing options near Spinney Mountain Reservoir and south of Hartsel. More description of each alternative is explained in the rest of the Permitting webpage copy.

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Proposed Wild Horse Reservoir Project

Aurora Water is proposing to build the Wild Horse Reservoir near Hartsel in Park County, Colo., approximately six miles west of Spinney Mountain Reservoir. This reservoir would be located in the South Platte River Basin as an “off-channel” facility, and would be filled through the existing Otero Pipeline using associated water rights.

The reservoir would cover a surface area of roughly 1,650 acres and provide approximately 90,000 acre-feet of active storage, held by three dams. Water would be transported to the reservoir using approximately three miles of new pipe that would connect to the existing Otero Pipeline. Water would then be sent to the Spinney Mountain Reservoir, which would be connected using approximately nine miles of new pipe.

Importantly, no new water rights or decrees are being sought for this proposed project.

The Wild Horse South Reservoir Alternative would consist of a reservoir with approximately 90,000 acre-feet of active storage capacity in Park County approximately 10 miles south of Hartsel, Colo., and approximately 6.5 miles south of the above proposed Wild Horse Reservoir site. The reservoir would be ‘off-channel’ and filled by the existing Otero Pipeline. Water would be transported through three miles of new pipeline from the existing Otero Pipeline. Releases from the reservoir would be piped to Spinney Mountain Reservoir through a 13-mile pipeline. The reservoir would require one dam. No new water rights or decrees are being pursued for this alternative.

The Small Wild Horse + Aquifer Storage and Recovery (ASR) Alternative would consist of (1) a reservoir with approximately 45,000 AF of active water storage capacity located in Park County, Colo., near Hartsel and about six miles west of Spinney Mountain Reservoir, and (2) an aquifer (underground deep wells) storage and pipe conveyance system located in Arapahoe County, Colo., approximately six miles north and eight miles west of Aurora Reservoir. The reservoir would be ‘off-channel’ and filled by the existing Otero Pipeline. Releases from the reservoir would be piped to Spinney Mountain Reservoir. No new water rights or decrees are being pursued for this alternative. New overhead power lines would be extended from a connection point near Hartsel to both the reservoir inlet and outlet valve houses.

The ASR system would require approximately 20 ASR wells and a network of pipelines for storage in the Denver Basin Aquifer. The ASR wells would be deep aquifer wells that would allow water to be injected and withdrawn from the aquifer. Water for the ASR system would be conveyed from the Rampart Delivery System to the existing Griswold Water Purification Facility (WPF) for treatment. A new pump station at Griswold WPF would pump the treated water through a bidirectional pipeline network to the ASR wells to inject for storage. The ASR wells would withdraw stored water as needed and pump the water back to Griswold WPF for treatment and distribution.

The existing Spinney Mountain Reservoir is located in Park County below the confluence of the Middle Fork and South Fork of the South Platte River, approximately three miles upstream from Eleven Mile Canyon Reservoir. It is an on-channel reservoir. The Spinney Mountain Reservoir Enlargement Alternative consists of increasing the storage capacity of the existing 56,000 AF Spinney Mountain Reservoir by 90,000 AF to a total of 146,000 AF. The Spinney Mountain Enlargement alternative would require the existing dam to either be raised by 25 feet or replaced with a new dam constructed downstream of the existing dam. A new saddle dam on the northern end of the reservoir would also be required to complete the enlargement.  No new water rights or decrees are being pursued for this alternative.

In the NEPA process, the No Action Alternative is a required baseline scenario that represents what would happen if the proposed project or action is not implemented. Aurora Water is still considering what measures it could pursue without a federal permit and right-of-way (ROW) grant from the BLM. A ROW grant from the BLM is required because the proposed Wild Horse Reservoir would inundate BLM-managed lands.

2025 Surveys to Support BLM Evaluation Process

With landowner permission, natural resource and cultural surveys will be conducted on the proposed project site and alternatives in 2025 from late April through August. Some landowners may be contacted to request permission to access private property for the surveys. This information is needed for the evaluations and disclosures mentioned above and will focus on areas that have not yet been assessed. These surveys will not damage property or involve any ground disturbance.

Wild Horse Reservoir State and Local Permitting

The project would also require dam safety, fish and wildlife, and highway crossing permits issued through the State of Colorado. Aurora would apply for a local Park County  1041 permit. The county would also need to approve rezoning as well as road relocation and improvements.

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