Twin Lakes Reservoir Report

Last Updated: December 5, 2025

Twin Lakes, located in Vilas County, Wisconsin, is a public utility hydroelectric facility with a primary purpose of flood risk reduction and hydroelectric power generation.


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Summary

The dam, completed in 1908, is a gravity structure measuring 10 feet in height and 157 feet in length, with a NID storage capacity of 93,526 acre-feet. The dam is equipped with a controlled spillway and a Tainter (radial) outlet gate to manage water flow and ensure safety.

Managed by the Federal Energy Regulatory Commission, Twin Lakes has a low hazard potential and a very high risk assessment rating due to its critical role in flood control and power generation. Although the condition assessment is not available, regular inspections are conducted every three years to ensure the dam's structural integrity and operational efficiency. The emergency action plan (EAP) for the dam was last revised in December 2018 to meet guidelines and enhance emergency preparedness.

With its picturesque location in Eagle River and important role in water resource management, Twin Lakes is a vital asset for the surrounding community and ecosystem. Climate and water resource enthusiasts can appreciate the engineering and environmental significance of this historic dam, which continues to play a crucial role in safeguarding the local area from flooding and providing clean energy through hydroelectric power generation.

Year Completed

1908

Dam Length

157

Dam Height

10

River Or Stream

Twin

Primary Dam Type

Gravity

Drainage Area

26

Nid Storage

93526

Outlet Gates

Tainter (radial) - 1

Hazard Potential

Low

Foundations

Soil

Nid Height

10
       
Seasonal Comparison

Weather Forecast

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.