Robinson #4 Reservoir Report
Nearby: Robinson #7 Robinson #8
Last Updated: December 6, 2025
Robinson #4 is a private dam located in Custer, Montana, specifically in the city of MIZPAH.
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Summary
Completed in 1940, this earth dam stands at a height of 33 feet and spans 500 feet in length. Its primary purposes include fire protection, stock, and serving as a small fish pond. The dam has a NID storage capacity of 146 acre-feet, with a normal storage level of 74 acre-feet.
Situated on TR-HERCULES CREEK, Robinson #4 is regulated by the Montana Department of Natural Resources and Conservation (DNRC), with state permitting, inspection, and enforcement in place. Despite being categorized as having low hazard potential, the dam's condition assessment is currently marked as "Not Rated." Emergency action plans and risk assessment measures have not been documented, raising potential concerns for water resource and climate enthusiasts interested in the safety and management of this dam. While the dam has not been modified in recent years, ongoing monitoring and maintenance may be necessary to ensure its long-term stability and functionality.
Year Completed |
1940 |
Dam Length |
500 |
Dam Height |
33 |
River Or Stream |
TR-HERCULES CREEK |
Primary Dam Type |
Earth |
Hydraulic Height |
33 |
Nid Storage |
146 |
Hazard Potential |
Low |
Nid Height |
33 |
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.
Robinson #4