Big St Germain Reservoir Report

Last Updated: December 5, 2025

Big St Germain is a hydroelectric dam located in Vilas, Wisconsin, along the St Germain River.


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Summary

Built in 1923, this Gravity-type dam stands at 7 feet tall and has a Hydraulic height of 4 feet, with a storage capacity of 33,655 acre-feet. The dam serves multiple purposes, including flood risk reduction and hydroelectric power generation, making it a valuable resource for the region.

Managed by the Federal Energy Regulatory Commission, Big St Germain has a low hazard potential and a high risk assessment rating. It is equipped with three slide gates for water release and has a spillway width of 19 feet. Despite its age, the dam's condition assessment is not available, and it was last inspected in June 2017. The emergency action plan was last revised in December 2018, highlighting the importance of preparedness and risk management for this critical infrastructure.

As a key feature in the Detroit District's water resource management, Big St Germain plays a vital role in maintaining water levels and providing clean energy to the surrounding area. With its historical significance and ongoing operational importance, this dam stands as a testament to the intersection of water resource management and climate resilience in the region.

Year Completed

1923

Dam Length

117

Dam Height

7

River Or Stream

St Germain River

Primary Dam Type

Gravity

Hydraulic Height

4

Drainage Area

73.1

Nid Storage

33655

Outlet Gates

Slide (sluice gate) - 3

Hazard Potential

Low

Foundations

Soil

Nid Height

7
       
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.