Tailings Impoundment Reservoir Report

Last Updated: December 5, 2025

The Tailings Impoundment in Madison, Montana is a privately owned structure regulated by the Montana Department of Environmental Quality (DEQ) for its significant hazard potential.


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Summary

This earth dam stands at a height of 155 feet and has a storage capacity of 200 acre-feet. While the dam was last inspected in 2009 and deemed to be in "Not Rated" condition, it is subject to state permitting, inspection, and enforcement to ensure public safety and environmental protection.

Located in Cardwell, Montana, the Tailings Impoundment poses a potential risk to communities downstream in the event of a failure. Despite lacking a formal emergency action plan (EAP) and risk assessment, the Mine Safety and Health Administration oversees inspections and operations to mitigate any hazards. As a key component of the Mine Safety and Health Administration's regulatory oversight, this dam serves as a crucial infrastructure for managing mining waste and protecting water resources in the area.

With its location in the Walla Walla District and the oversight of federal and state agencies, the Tailings Impoundment's importance in the regional water management system cannot be understated. As water resource and climate enthusiasts, understanding the complexities of maintaining and regulating such structures is essential for ensuring the safety and sustainability of our natural environment in the face of potential hazards and climate challenges.

Dam Height

155

Primary Dam Type

Earth

Nid Storage

200

Hazard Potential

Significant

Nid Height

155
       
Seasonal Comparison

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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.