Stillwater Hertzler Tailings Dam Reservoir Report

Reservoir Report

Montana

Nearby: Stillwater Nye Tailings Dam Ernie Hudson

Last Updated: December 4, 2025

The Stillwater Hertzler Tailings Dam in Stillwater, Montana, is a privately owned structure regulated by the state's Department of Environmental Quality.

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Summary

This dam, with a storage capacity of 460 acre-feet, primarily serves the purpose of managing tailings from mining operations in the area. Despite its high hazard potential, the dam is currently in satisfactory condition, as assessed in June 2018, with regular inspections conducted every 5 years.

Located in Congressional District 00, Montana, this tailings dam is under the jurisdiction of the Mine Safety and Health Administration for regulatory oversight and inspections. The dam's emergency action plan was last revised in March 2016, and there are no inundation maps or risk assessments publicly available for this structure. With a surface area of 532 acres and normal storage capacity of 153 acre-feet, the Stillwater Hertzler Tailings Dam plays a crucial role in managing mining waste in the region while adhering to state permitting and inspection requirements.

Surface Area	532
Nid Storage	460
Hazard Potential	High

Seasonal Comparison

Weather Forecast

Nearby Streamflow Levels

West Rosebud Creek Near Roscoe Mt 73.3cfs	73cfs
Stillwater River Near Absarokee Mt 488.0cfs	488cfs
Red Lodge Cr Ab Cooney Re Nr Boyd Mt 41.1cfs	41cfs
Willow Creek Near Boyd Mt 20.0cfs	20cfs
Boulder River At Big Timber Mt 210.0cfs	210cfs
Soda Butte Cr At Park Bndry At Silver Gate 6.92cfs	7cfs

Dam Data Reference

Condition Assessment

Satisfactory
No 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

High
Dams 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.