Middle Piney Lake Dam Reservoir Report

Last Updated: December 27, 2025

Middle Piney Lake Dam, located in Big Piney, Wyoming, is a Federal-owned structure managed by the Forest Service.


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Summary

Built in 1940, this Earth-type dam stands at a height of 24 feet and stretches 125 feet in length, creating a reservoir with a storage capacity of 4,389 acre-feet. The primary purpose of the dam is for recreation, providing opportunities for outdoor enthusiasts to enjoy the picturesque surroundings of Middle Piney Creek.

Despite its scenic appeal, Middle Piney Lake Dam has a high hazard potential and a poor condition assessment, with the last inspection conducted in October 2017. The dam's spillway is uncontrolled, and the risk assessment indicates a moderate level of risk. Despite these challenges, the Forest Service continues to oversee the operation and maintenance of the dam, ensuring the safety of the surrounding community and the preservation of this vital water resource in Sublette County.

Water resource and climate enthusiasts will find Middle Piney Lake Dam to be a fascinating example of the delicate balance between human intervention and natural ecosystems. As efforts are made to address the dam's condition and ensure its long-term stability, it serves as a reminder of the importance of responsible dam management in the face of changing environmental conditions and increasing demands on water resources.

Year Completed

1940

Dam Length

125

Dam Height

24

River Or Stream

MIDDLE PINEY CREEK

Primary Dam Type

Earth

Surface Area

200

Hydraulic Height

23

Drainage Area

6

Nid Storage

4389

Structural Height

24

Outlet Gates

Uncontrolled

Hazard Potential

High

Foundations

Unlisted/Unknown

Nid Height

24
       
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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.