Halfpint Detention Dam Reservoir Report
Last Updated: December 21, 2025
Halfpint Detention Dam, located in Nashua, Montana, along the Willow Creek/Milk River, is a gravity-type structure primarily designed for flood risk reduction.
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Summary
Constructed in 1965 by the Bureau of Land Management, this Federal-owned dam stands at a structural height of 32 feet and has a hydraulic height of 21 feet, with a total length of 1005 feet. It has a storage capacity of 275 acre-feet, serving to mitigate potential risks associated with its low hazard potential.
Despite its vital role in flood risk reduction, Halfpint Detention Dam currently has a poor condition assessment, with a moderate risk rating of 3 out of 5. The dam is under the jurisdiction of the Department of Natural Resources and Conservation in Montana, with regular state inspections and enforcement in place. Although the dam has not been modified in recent years, its emergency action plan and risk management measures are not fully up to date, highlighting the need for improved readiness and preparedness for potential hazards. For water resource and climate enthusiasts, the Halfpint Detention Dam serves as a critical infrastructure in the region, warranting attention and investment to ensure its continued effectiveness in safeguarding the surrounding areas from flood risks.
Year Completed |
1965 |
Dam Length |
1005 |
River Or Stream |
WILLOW CK./MILK RIVER |
Primary Dam Type |
Gravity |
Surface Area |
59.54 |
Hydraulic Height |
21 |
Drainage Area |
16.7 |
Nid Storage |
275 |
Structural Height |
32 |
Hazard Potential |
Low |
Foundations |
Unlisted/Unknown |
Nid Height |
32 |
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.
Halfpint Detention Dam