Hill #2 Reservoir Report

Last Updated: December 5, 2025

Hill #2, located in Mosby, Montana, is a privately owned irrigation dam designed by the USDA NRCS and regulated by the DNRC.


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Summary

Completed in 1954, this earth dam stands at a height of 25 feet and has a storage capacity of 175 acre-feet, primarily for irrigation purposes along the Shaw Coulee river. With a low hazard potential and a moderate risk assessment rating, Hill #2 serves as a crucial water resource for the surrounding area.

Managed by the Natural Resources Conservation Service, this dam plays a vital role in water management and agricultural activities in Garfield County. Despite its age, the condition of Hill #2 has not been officially rated, highlighting the need for continued monitoring and maintenance to ensure its long-term functionality. With a spillway width of 100 feet and a maximum discharge of 500 cubic feet per second, this structure is well-equipped to handle potential flooding events while providing reliable water supply for local farmers and residents.

As climate change continues to impact water resources and weather patterns, the importance of infrastructure like Hill #2 in sustainable water management cannot be overstated. With its strategic location and design, this dam stands as a testament to the collaboration between federal and state agencies in safeguarding water resources for future generations.

Year Completed

1954

Dam Length

800

Dam Height

25

River Or Stream

SHAW COULEE

Primary Dam Type

Earth

Hydraulic Height

25

Drainage Area

46.88

Nid Storage

175

Hazard Potential

Low

Nid Height

25
       
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.