Arnault Branch Mine Dam Reservoir Report

Last Updated: December 5, 2025

Arnault Branch Mine Dam, located in Old Mines, Missouri, is a privately owned structure that serves as a tailings dam along the tributary of Arnault Creek.


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Summary

Completed in 1970, this rockfill dam stands at a height of 46 feet and has a length of 750 feet, providing storage for up to 582 acre-feet of water. The dam, regulated by the DAM AND RESERVOIR SAFETY PROG in Missouri, has a high hazard potential due to its location and purpose.

Despite its satisfactory condition assessment as of 2008, the dam is subject to regular inspections every three years to ensure its safety and stability. With a moderate risk assessment rating of 3, it is crucial for the owners and regulatory agencies to implement necessary risk management measures to prevent any potential disasters. The dam's spillway is uncontrolled with a width of 10 feet, and it has a maximum discharge capacity of 2375 cubic feet per second.

Water resource and climate enthusiasts will find Arnault Branch Mine Dam to be an intriguing structure with a significant impact on the surrounding environment and water resources. Its unique design and purpose as a tailings dam provide insights into the intersection of mining activities and water management. With its high hazard potential and moderate risk assessment, this dam serves as a reminder of the importance of proper maintenance and regulation to prevent any potential threats to the area.

Year Completed

1970

Dam Length

750

Dam Height

46

River Or Stream

TRIB-ARNAULT CREEK

Surface Area

41

Drainage Area

543

Nid Storage

582

Structural Height

46

Outlet Gates

None

Hazard Potential

High

Foundations

Unlisted/Unknown

Nid Height

46
       
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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.