PERMITTING

Wild Horse Reservoir Federal Permitting

The proposed Wild Horse Reservoir project is currently in the planning and pre-permitting phase. The Bureau of Land Management (BLM), as the lead federal agency, is managing the federal National Environmental Policy Act (NEPA) process and will prepare an Environmental Impact Statement (EIS), which is a public-facing, comprehensive analysis of the potential environmental and social impacts from Wild Horse Reservoir. The NEPA process is expected to formally begin in 2026 and take about two years to complete. BLM will host public scoping meetings and accept public comments from interested parties during the NEPA process.

In the NEPA process, BLM plans to analyze:

  • Wild Horse Reservoir (known as the proposed action)
  • Wild Horse South Reservoir Alternative
  • Small Wild Horse Reservoir + Denver Basin Aquifer Storage and Recovery (ASR) Alternative
  • Spinney Mountain Reservoir Enlargement Alternative
  • No Action Alternative—Denver Basin ASR (if the proposed action is not approved)

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.

Click for larger image

Proposed Wild Horse Reservoir Project

Aurora Water is proposing to build the Wild Horse Reservoir approximately six miles west of Spinney Mountain Reservoir near Hartsel, Colo., in Park County. The reservoir—which would cover a surface area of approximately 1,700 acres and store approximately 90,000 acre-feet of water—would be off channel, meaning it would not have any river or stream flowing into or out of it. Water would be supplied into the reservoir through a new inlet pipeline connected to the existing Otero pipeline. A new outlet pipeline would transport water from Wild Horse Reservoir to Spinney Mountain Reservoir as needed.

Importantly, water stored in the proposed reservoir would be supplied from Aurora Water’s existing Colorado and Arkansas River water rights so no new water rights or decrees would be required.

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

The Small Wild Horse + Denver Basin Aquifer Storage and Recovery (ASR) Alternative would consist of:

  1. A reservoir storing approximately 45,000 acre-feet of water located about six miles west of Spinney Mountain Reservoir near Hartsel, Colo., in Park County.
  2. An aquifer (underground deep wells) storage and pipe conveyance system located within the city of Aurora in Adams and Arapahoe counties, Colo.

The smaller reservoir would be off channel and supplied by the existing Otero pipeline. Releases from the reservoir would be piped to Spinney Mountain Reservoir. No new water rights or decrees would be 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 21 ASR well sites 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. The proposed ASR well sites would be located along the linear portions of the ASR system. A new pump station at Griswold Water Purification Facility (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 then pump the water to a desalination facility for treatment and 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. The Spinney Mountain Reservoir Enlargement Alternative consists of increasing the storage capacity of the existing on-channel (South Platte River) reservoir by an additional 135,000 acre-feet to a total of 189,000 acre-feet. The Spinney Mountain Enlargement alternative would require the existing dam to either be raised by 22 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 would be pursued for this alternative.

The No Action Alternative consists of an ASR system located within the City of Aurora in Adams and Arapahoe counties, Colo. The ASR system would require 21 ASR well sites and a network of pipelines for storage in the Denver Basin Aquifer. The ASR wells would be deep aquifer wells that allow water to be injected and withdrawn from the aquifer. The proposed 21 ASR well sites would be located along the linear portions of the ASR system. A new pump station at Griswold Water Purification Facility (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 then pump the water to a desalination facility for treatment and back to Griswold WPF for treatment and distribution.

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, among others. Aurora Water would apply for a local Park County 1041 permit. The county would also need to approve rezoning and road realignment and improvements for County Road (CR) 53.

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