Thomson Dam No. 9 Reservoir Report

Last Updated: December 5, 2025

Thomson Dam No.


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Summary

9, located in Thomson, Minnesota, stands as a vital structure along the St. Louis River, serving multiple purposes including hydroelectric power generation and recreation. Completed in 1907, this gravity dam stands at a height of 11 feet and has a length of 100 feet, with a storage capacity of 4,352 acre-feet. The dam is under the jurisdiction of the Minnesota Department of Natural Resources and is regulated by the Federal Energy Regulatory Commission.

With its high hazard potential, Thomson Dam No. 9 is subject to regular state inspections and enforcement to ensure its safety and integrity. The dam is part of a network of 13 associated structures, contributing to the management of water resources in the area. The location of the dam in Carlton County, Minnesota, highlights its significance in water resource management and climate resilience efforts in the region.

Managed by the St. Paul District of the US Army Corps of Engineers, Thomson Dam No. 9 plays a crucial role in water storage and flow regulation along the St. Louis River. Its history, design, and purpose make it a key asset for both water management and recreational activities, showcasing the intersection of human infrastructure and natural resources in the context of climate change and sustainable development.

Year Completed

1907

Dam Length

100

Dam Height

11

River Or Stream

St Louis River

Surface Area

375

Hydraulic Height

11

Nid Storage

4352

Structural Height

11

Hazard Potential

High

Nid Height

11
       
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.