Empire Mine Expanded Tertiary Dam Reservoir Report

Last Updated: December 5, 2025

The Empire Mine Expanded Tertiary Dam, also known as the ETB Tertiary Expansion Dam, is a privately-owned structure located in Austin, Michigan.


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Summary

Completed in 1985, this Earth-type dam stands at a height of 52 feet and spans 550 feet in length, with a primary purpose of storing tailings from mining activities. Situated on Green Creek, in Marquette County, this dam has a significant hazard potential but is currently assessed to be in satisfactory condition.

Managed by the Mine Safety and Health Administration, the Empire Mine Expanded Tertiary Dam has a storage capacity of up to 1483 acre-feet and a surface area of 108 acres. It features a controlled spillway with a width of 6 feet, ensuring proper water flow management. Despite its very high risk assessment, regular inspections are conducted to ensure the dam's continued safety and integrity. With its strategic location and vital role in industrial operations, the Empire Mine Expanded Tertiary Dam is a crucial asset in water resource management and climate resilience efforts in the region.

Year Completed

1985

Dam Length

550

Dam Height

52

River Or Stream

Green Creek

Primary Dam Type

Earth

Surface Area

108

Hydraulic Height

47

Nid Storage

1483

Structural Height

52

Hazard Potential

Significant

Foundations

Unlisted/Unknown

Nid Height

52
       
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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.