Cooney Reservoir Report

Last Updated: December 5, 2025

Cooney Dam, located in Carbon County, Montana, is a state-regulated structure on the Red Lodge Creek, built in 1937 primarily for irrigation purposes.


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Summary

With a dam height of 102 feet and a storage capacity of 28,230 acre-feet, it plays a crucial role in water resource management in the region. The dam has a surface area of 1,078 acres and a drainage area of 206 square miles, ensuring a steady supply of water for agricultural activities in the area.

Despite being classified as having a high hazard potential, Cooney Dam is in satisfactory condition as of the last assessment in December 2020. Regular inspections are conducted, with the last one taking place in November 2021, to ensure the safety and integrity of the structure. The dam has an uncontrolled spillway with a width of 150 feet, and outlet gates are also uncontrolled. While the risk assessment is moderate, with a rating of 3, it is essential to continue monitoring and implementing risk management measures to mitigate any potential threats and ensure the long-term sustainability of this vital water resource infrastructure in Montana.

Year Completed

1937

Dam Length

2369

Dam Height

102

River Or Stream

RED LODGE CREEK

Primary Dam Type

Earth

Surface Area

1078

Hydraulic Height

102

Drainage Area

206

Nid Storage

28230

Outlet Gates

Uncontrolled

Hazard Potential

High

Foundations

Rock

Nid Height

102
       
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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.