Boulder Lake Reservoir Report

Last Updated: December 5, 2025

Boulder Lake, located in Cloquet, Minnesota, is a picturesque reservoir with a rich history dating back to its completion in 1919.


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Summary

Managed by the Federal Energy Regulatory Commission, this hydroelectric dam serves multiple purposes, including providing recreational opportunities for visitors. The dam, consisting of concrete, earth, and multi-arch structures, stands at a height of 20 feet and spans 1470 feet in length.

With a storage capacity of 30,300 acre-feet and a normal storage of 29,440 acre-feet, Boulder Lake covers a surface area of 4100 acres and has a drainage area of 63 square miles. The controlled spillway, with a width of 8 feet, ensures the safe management of water levels, while the low hazard potential and regular inspections contribute to its overall safety. Despite facing a very high risk assessment, the dam's emergency action plan is up to date, reflecting its commitment to preparedness and risk management.

Boulder Lake's association with Otter Creek adds to its charm, attracting water resource and climate enthusiasts seeking to explore the surrounding St. Louis County area. With its blend of historical significance, recreational offerings, and environmental stewardship, Boulder Lake stands as a testament to the enduring relationship between nature and infrastructure in the heart of Minnesota.

Year Completed

1919

Dam Length

1470

Dam Height

20

River Or Stream

Otter Creek

Surface Area

4100

Drainage Area

63

Nid Storage

30300

Outlet Gates

Slide (sluice gate) - 1

Hazard Potential

Low

Nid Height

20
       
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.