Loon Lake Twp 16 Reservoir Report

Last Updated: December 5, 2025

Loon Lake Twp 16, located in Cass County, Minnesota, is a state-regulated dam with a primary purpose of "Other." Built in 1978 and designed by the NRCS, this rockfill dam stands at a height of 10 feet and stretches 160 feet in length along Mayo Creek.


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Summary

It has a storage capacity of 1000 acre-feet and a low hazard potential rating.

Despite its poor condition assessment in 2015, the dam remains under state jurisdiction and is subject to regular inspections, enforcement, and permitting by the Minnesota Department of Natural Resources, Environmental & Water Resources division. With a drainage area of 5 square miles and a maximum discharge rate of 339 cubic feet per second, this dam plays a vital role in managing water resources in the surrounding area.

For water resource and climate enthusiasts, Loon Lake Twp 16 serves as a fascinating case study in dam infrastructure and regulation. Its location in the St. Paul District, along with its historical significance and ongoing management, make it a valuable asset in understanding the intersection of water management, environmental protection, and public safety in the state of Minnesota.

Year Completed

1978

Dam Length

160

Dam Height

6

River Or Stream

MAYO CREEK

Primary Dam Type

Rockfill

Drainage Area

5

Nid Storage

1000

Structural Height

10

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

10
       
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.