Sheep Mountain Reservoir Report

Last Updated: December 5, 2025

Sheep Mountain, also known as the Illegal Dam, is a privately owned structure located in Slater, Colorado.


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Summary

Built in 1946, this earth dam on Spring Creek serves primarily for irrigation purposes in Carbon, Wyoming. With a height of 40 feet and a length of 610 feet, Sheep Mountain has a storage capacity of 438 acre-feet and a surface area of 35 acres.

Despite its low hazard potential, Sheep Mountain's condition assessment is rated as poor, with the last inspection conducted in September 2020. The dam's spillway is uncontrolled, and it has one valve outlet gate. While it has a moderate risk rating of 3, the dam is state-regulated and routinely inspected, meeting guidelines for emergency action preparedness. With its stone core and soil foundation, Sheep Mountain stands as a testament to early 20th-century irrigation infrastructure in the region, showcasing the intersection of water resource management and climate adaptation efforts.

Year Completed

1946

Dam Length

610

Dam Height

40

River Or Stream

SPRING CREEK

Primary Dam Type

Earth

Surface Area

35

Hydraulic Height

33

Nid Storage

438

Structural Height

42

Outlet Gates

Valve - 1

Hazard Potential

Low

Foundations

Soil

Nid Height

42
       
Seasonal Comparison

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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.