Pr-40 Retention Dam Reservoir Report
Nearby: De Puydt Nelson Dike D
Last Updated: December 6, 2025
Located in Hinsdale, Montana, the Pr-40 Retention Dam is a crucial water resource managed by the Bureau of Land Management.
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Summary
Built in 1942, this gravity dam stands at a structural height of 18 feet and has a hydraulic height of 14 feet, serving multiple purposes such as fire protection, stock, and small fish pond. With a storage capacity of 127.69 acre-feet and covering a surface area of 22.6 acres, this dam plays a vital role in managing water resources in the region.
The Pr-40 Retention Dam is situated on the Larb Creek/Milk River and has a low hazard potential. Despite not being rated for its condition, the dam underwent its last inspection in August 2016 with a scheduled inspection frequency of 5 years. While the dam does not have an emergency action plan in place, it remains under the jurisdiction of the Bureau of Land Management, ensuring continued oversight and management to mitigate any potential risks or hazards associated with the structure.
Water resource and climate enthusiasts will appreciate the historical significance and functional importance of the Pr-40 Retention Dam in sustaining water supply, protecting against wildfires, and supporting local ecosystems. As part of the larger network of water infrastructure in Montana, this dam stands as a testament to effective resource management and proactive measures taken to ensure the safety and sustainability of water resources in the region.
Year Completed |
1942 |
Dam Length |
357 |
River Or Stream |
LARB CK./MILK RIVER |
Primary Dam Type |
Gravity |
Surface Area |
22.6 |
Hydraulic Height |
14 |
Drainage Area |
0.3 |
Nid Storage |
127.69 |
Structural Height |
18 |
Hazard Potential |
Low |
Foundations |
Unlisted/Unknown |
Nid Height |
18 |
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.
Pr-40 Retention Dam