Sullivan Lake Reservoir Report

Last Updated: December 5, 2025

Sullivan Lake, located in the heart of Superior National Forest in Minnesota, is a picturesque water resource that serves multiple purposes including recreation, fish and wildlife pond, and flood risk reduction.


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Summary

Managed by the Forest Service, this Earth dam structure stands at a height of 7 feet with a hydraulic height of 8 feet, completed in the year 1900. The lake has a storage capacity of 250 acre-feet, with a normal storage of 200 acre-feet, and covers a surface area of 41 acres with a drainage area of 4 square miles.

The dam, built on Sullivan Creek, spans 800 feet in length and features an uncontrolled spillway with a width of 180 feet, ensuring a maximum discharge of 100 cubic feet per second. Despite its low hazard potential and moderate risk assessment, the condition of the dam is currently not rated, with the last inspection conducted in May 2017. With its tranquil surroundings and vital role in the local ecosystem, Sullivan Lake remains a key resource for water and climate enthusiasts to appreciate and monitor for its continued functionality and environmental impact.

Year Completed

1900

Dam Length

800

Dam Height

7

River Or Stream

SULLIVAN CREEK

Primary Dam Type

Earth

Surface Area

41

Hydraulic Height

8

Drainage Area

4

Nid Storage

250

Structural Height

7

Hazard Potential

Low

Foundations

Soil

Nid Height

8
       
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.