Westermark Reservoir Report
Nearby: Mccracken Brothers German Reservoir
Last Updated: December 5, 2025
Westermark is a privately owned recreational dam located in Toole, Montana, along the TR-MARIAS RIVER.
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Summary
Built in 1964 by the USDA NRCS, this earth dam stands at a height of 45 feet and has a length of 360 feet, providing a maximum storage capacity of 131 acre-feet. The dam serves the primary purpose of recreation and is regulated by the DNRC, with inspection, permitting, and enforcement measures in place to ensure its safety and compliance with state regulations.
With a low hazard potential and a moderate risk assessment rating, Westermark dam is considered to be in satisfactory condition, though it has not been officially rated. The spillway type is uncontrolled, with a width of 40 feet, and the dam has a drainage area of 0.47 square miles. While it has not undergone any modifications or been assessed for emergency preparedness, the dam is equipped to handle a maximum discharge of 240 cubic feet per second, ensuring the safety of downstream communities in the event of excess water flow. For water resource and climate enthusiasts, Westermark dam offers a fascinating example of how private owners and state agencies work together to manage and maintain crucial water infrastructure for both recreational and safety purposes in Montana.
Year Completed |
1964 |
Dam Length |
360 |
Dam Height |
45 |
River Or Stream |
TR-MARIAS RIVER |
Primary Dam Type |
Earth |
Hydraulic Height |
45 |
Drainage Area |
0.47 |
Nid Storage |
131 |
Hazard Potential |
Low |
Nid Height |
45 |
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.
Westermark