Sheepshed Detention Dam Reservoir Report
Last Updated: December 21, 2025
Sheepshed Detention Dam, located in Nashua, Montana, is a federal-owned structure managed by the Bureau of Land Management.
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Summary
Built in 1954, the primary purpose of this gravity dam is flood risk reduction along Willow Creek and the Milk River. With a height of 27 feet and a hydraulic height of 20 feet, the dam has a storage capacity of 343 acre-feet and covers a surface area of 56.45 acres.
Despite its low hazard potential, the dam's condition is currently assessed as unsatisfactory, with the last inspection conducted in December 2019. The risk assessment for Sheepshed Detention Dam is moderate, suggesting a need for risk management measures to ensure its continued safety and functionality. While the dam lacks an Emergency Action Plan and inundation maps, it is important to continuously monitor and maintain this critical infrastructure to prevent any potential risks or hazards.
As a key component in the flood risk reduction efforts in the area, Sheepshed Detention Dam plays a crucial role in protecting the surrounding community from potential flood events. With its location in a high-risk area, it is essential for authorities to prioritize regular inspections, maintenance, and the development of an Emergency Action Plan to mitigate any potential risks and ensure the safety of the residents and infrastructure downstream.
Year Completed |
1954 |
Dam Length |
1410 |
River Or Stream |
WILLOW CK./MILK RIVER |
Primary Dam Type |
Gravity |
Surface Area |
56.45 |
Hydraulic Height |
20 |
Drainage Area |
4.5 |
Nid Storage |
343 |
Structural Height |
27 |
Hazard Potential |
Low |
Foundations |
Unlisted/Unknown |
Nid Height |
27 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Sheepshed Detention Dam