Thomson Dam No 12 Reservoir Report

Last Updated: December 5, 2025

Thomson Dam No 12, located in Duluth, Minnesota, is a vital structure in the management of the St.


°F

°F

mph

Wind

%

Humidity

Summary

Louis River. Completed in 1907, this earth dam stands at a height of 12 feet and has a length of 450 feet, providing hydroelectric power generation along with recreational opportunities. With a storage capacity of 4352 acre-feet and a surface area of 375 acres, Thomson Dam No 12 plays a significant role in water resource management in the region.

Managed by the Federal Energy Regulatory Commission, Thomson Dam No 12 is subject to regular inspections to ensure its safety and functionality. The dam has a high hazard potential, highlighting the importance of proper risk assessment and management measures. Despite its age, Thomson Dam No 12 continues to serve its purpose efficiently, contributing to the water supply and energy needs of the local community.

As a key component of the water infrastructure in Carlton County, Thomson Dam No 12 is a critical asset for both water resource management and climate resilience efforts. Its strategic location and design make it a valuable resource for both hydroelectric power generation and recreational activities. With ongoing regulatory oversight and maintenance, Thomson Dam No 12 remains a cornerstone of the region's water management system, ensuring the continued safety and sustainability of the St. Louis River ecosystem.

Year Completed

1907

Dam Length

450

Dam Height

12

River Or Stream

St Louis River

Surface Area

375

Hydraulic Height

12

Nid Storage

4352

Structural Height

12

Hazard Potential

High

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.