Toprail Dam Reservoir Report
Last Updated: December 20, 2025
Toprail Dam, located in Valley County, Montana, is a Federal-owned structure managed by the Bureau of Land Management.
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Summary
This gravity dam, with a height of 20 feet and a hydraulic height of 15 feet, was designed using buttress and stone core types. It has a storage capacity of 55.53 acre-feet and covers a surface area of 10.34 acres, serving as a crucial water resource in the region.
Despite its low hazard potential, Toprail Dam has been assessed as unsatisfactory in condition, indicating a need for maintenance and improvements. The dam features an uncontrolled spillway with a width of 1 foot and has not been modified in recent years. With a moderate risk rating of 3, it is important for water resource and climate enthusiasts to monitor the dam's condition and management measures to ensure its continued safety and functionality.
The dam's last inspection was conducted in August 2016, with an inspection frequency of 5 years. While the dam does not have a state regulatory agency overseeing its operations, the Bureau of Land Management is responsible for its construction, inspections, and operations. As an intermittent structure on an unnamed river or stream, Toprail Dam plays a vital role in water management in the area and warrants ongoing attention and maintenance to address its current unsatisfactory condition and moderate risk level.
Dam Length |
616 |
River Or Stream |
Intermittent |
Primary Dam Type |
Gravity |
Surface Area |
10.34 |
Hydraulic Height |
15 |
Drainage Area |
0.2 |
Nid Storage |
55.53 |
Structural Height |
20 |
Hazard Potential |
Low |
Foundations |
Unlisted/Unknown |
Nid Height |
20 |
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.
Toprail Dam