Thomson Dam No 8 Reservoir Report

Last Updated: December 5, 2025

Thomson Dam No 8, located in Thomson, Minnesota, is a key structure along the St.


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Summary

Louis River designed primarily for hydroelectric power generation and recreational activities. Built in 1907, this earth and gravity dam stands at a height of 12 feet and spans 100 feet in length, with a storage capacity of 4352 acre-feet and a surface area of 375 acres. Despite being regulated by the State of Minnesota and the Federal Energy Regulatory Commission, the dam has a low hazard potential and undergoes inspections every three years to ensure its structural integrity.

With a total of 13 associated structures, including various reservoirs and outlets, Thomson Dam No 8 plays a crucial role in water resource management in the region. The dam is situated in Carlton County, Minnesota, under the jurisdiction of the St. Paul District of the US Army Corps of Engineers. Despite its age, the dam remains a vital component of the local water infrastructure, supporting both energy production and recreational opportunities for residents and visitors alike.

In the event of an emergency, the dam has an Emergency Action Plan (EAP) in place, last revised in 2001, to guide response efforts and ensure public safety. While the condition assessment of the dam is currently not available, regular inspections and risk assessments are conducted to monitor its performance and identify any potential issues. Overall, Thomson Dam No 8 stands as a testament to the enduring importance of water resource management and climate resilience in the face of changing environmental conditions.

Year Completed

1907

Dam Length

100

Dam Height

12

River Or Stream

St Louis River

Surface Area

375

Hydraulic Height

12

Nid Storage

4352

Structural Height

12

Hazard Potential

Low

Nid Height

12
       
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.