Thomson Dam No 2a & 2b Reservoir Report

Last Updated: December 5, 2025

Thomson Dam No 2a & 2b, located in Carlton, Minnesota, along the St.


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Summary

Louis River, is a captivating structure with a rich history dating back to its completion in 1907. This gravity and rockfill dam stands at a height of 23 feet and stretches 530 feet in length, providing hydroelectric power and recreational opportunities. With a maximum storage capacity of 4,352 acre-feet, the dam serves as a vital resource for water management in the region.

Managed by the Federal Energy Regulatory Commission, Thomson Dam No 2a & 2b is subject to regular state inspections, regulations, and enforcement to ensure its safety and efficiency. The dam's high hazard potential underscores the importance of maintaining its structural integrity and emergency preparedness. Additionally, its risk assessment highlights the need for robust risk management measures to mitigate potential threats and ensure the safety of surrounding communities.

As a key component of the water infrastructure in the area, Thomson Dam No 2a & 2b plays a crucial role in supporting the region's energy needs and providing recreational opportunities. With its historical significance, impressive design, and essential functions, this dam stands as a testament to the intersection of water resource management, climate resilience, and infrastructure development in Minnesota.

Year Completed

1907

Dam Length

530

Dam Height

23

River Or Stream

St Louis River

Surface Area

375

Nid Storage

4352

Structural Height

23

Hazard Potential

High

Nid Height

23
       
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.