The Man Dam Reservoir Report
Nearby: Chapman Dam Sweet Carolyn
Last Updated: December 20, 2025
The Man Dam, located in Valley, Montana, is a Federal-owned structure managed by the Bureau of Land Management.
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Summary
This gravity dam, made of buttress and stone core types, stands at a structural height of 22 feet and has a hydraulic height of 17 feet. With a length of 470 feet, the dam provides a storage capacity of 58.76 acre-feet and covers a surface area of 8.59 acres. Despite being an intermittent river dam with low hazard potential, the Man Dam has not been rated for its condition.
The dam, constructed by the Bureau of Land Management, serves no specified primary purpose and lacks associated structures or outlet gates. It is situated in an area where inspection occurs every five years, with the last one conducted in September 2019. While the dam meets guidelines for emergency action plans and inundation maps, further risk assessment and management measures are yet to be determined. This unique structure, nestled in the Montana landscape, offers a fascinating case study for water resource and climate enthusiasts interested in the management of Federal-owned dams.
Dam Length |
470 |
River Or Stream |
INTERMITTENT |
Primary Dam Type |
Gravity |
Surface Area |
8.59 |
Hydraulic Height |
17 |
Drainage Area |
1 |
Nid Storage |
58.76 |
Structural Height |
22 |
Hazard Potential |
Low |
Foundations |
Unlisted/Unknown |
Nid Height |
22 |
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.
The Man Dam