Eleven Mile Canyon Reservoir Report

Last Updated: December 5, 2025

Eleven Mile Canyon is a concrete dam located in Park County, Colorado, serving as a vital water supply source in the region.


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Summary

Completed in 1932, this dam stands at a height of 128 feet, with a hydraulic height of 126 feet and a structural height of 151 feet. It has a storage capacity of 128,000 acre-feet and a normal storage level of 97,800 acre-feet, covering a surface area of 3,500 acres. The dam is situated on the South Platte River, managed by the Department of Water Resources (DWR) in Colorado.

With a high hazard potential but a satisfactory condition assessment as of June 2020, Eleven Mile Canyon is a crucial infrastructure for water resource management in the area. The dam's spillway is uncontrolled, with a width of 75 feet, and it has a maximum discharge capacity of 3,500 cubic feet per second. The risk assessment for the dam is moderate, indicating the need for ongoing monitoring and maintenance to ensure its safety and reliability for the community it serves. The dam is regulated, permitted, inspected, and enforced by the state of Colorado, demonstrating a commitment to upholding stringent safety standards and protocols.

Eleven Mile Canyon offers a glimpse into the intersection of water resource management and climate adaptation efforts in Colorado. As a primary water supply structure, it plays a vital role in ensuring water security for the region. With its historical significance and ongoing monitoring and maintenance efforts, the dam stands as a testament to the importance of sustainable water infrastructure in the face of evolving climate challenges.

Year Completed

1932

Dam Length

375

Dam Height

128

River Or Stream

SOUTH PLATTE RIVER

Primary Dam Type

Concrete

Surface Area

3500

Hydraulic Height

126

Drainage Area

963

Nid Storage

128000

Structural Height

151

Hazard Potential

High

Nid Height

151
       
Seasonal Comparison

Weather Forecast

Dam Data Reference

Condition Assessment

Satisfactory
No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.

Hazard Potential Classification

High
Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.