Grass Lake Reservoir Report

Last Updated: December 5, 2025

Grass Lake in Cass, Minnesota, is a Federal-owned Fish and Wildlife Pond managed by the USDA Forest Service.


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Summary

Built in 1970, this Earth dam stands at 5 feet tall and spans 350 feet in length, with a storage capacity of 135 acre-feet. The lake covers a surface area of 35 acres and serves as a vital habitat for local flora and fauna.

Despite its low hazard potential, Grass Lake has a moderate risk assessment rating, emphasizing the need for ongoing monitoring and risk management measures. While the dam's condition is currently not rated, regular inspections are conducted every 10 years to ensure its structural integrity. The outlet gates, spillway type, and emergency action plan status are not specified, highlighting areas for potential improvement in the future.

Located along the TR-Mississippi River, Grass Lake plays a crucial role in water resource management and conservation efforts in the region. Enthusiasts interested in climate resilience and the protection of aquatic ecosystems will find this picturesque lake a valuable case study in sustainable dam operation and maintenance practices.

Year Completed

1970

Dam Length

350

Dam Height

5

River Or Stream

TR-MISSISSIPPI RIVER

Primary Dam Type

Earth

Surface Area

35

Hydraulic Height

4

Drainage Area

1

Nid Storage

135

Structural Height

8

Hazard Potential

Low

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.