Lower Long Lake Dam Reservoir Report

Last Updated: December 5, 2025

Lower Long Lake Dam, located in Millville, Michigan, is a state-regulated earth dam completed in 1965 for the primary purpose of recreation.


°F

°F

mph

Wind

%

Humidity

Summary

The dam, standing at 11 feet tall with a hydraulic height of 9.3 feet, controls the flow of the Abbott Drain and creates a reservoir with a normal storage capacity of 600 acre-feet. With a surface area of 285 acres and a drainage area of 4.5 square miles, the dam has a low hazard potential and is currently in fair condition according to the last inspection conducted in May 2020.

Despite its low hazard potential, Lower Long Lake Dam poses a very high risk (ranked 1 out of 10) according to risk assessment criteria. The dam has a controlled spillway with a width of 5 feet and a maximum discharge capacity of 100 cubic feet per second. While the dam has not been significantly modified over the years and does not have associated locks or outlet gates, it undergoes regular inspections by the state regulatory agency, Michigan DEGLE, to ensure its structural integrity and safety. The dam's emergency action plan status and risk management measures are currently not reported, indicating potential areas for improvement in emergency preparedness.

Overall, Lower Long Lake Dam serves as a recreational resource for the local community, offering opportunities for boating, fishing, and other water activities. As an earth dam with a modest height and storage capacity, the dam plays a vital role in flood control and water management in the area. With its relatively low hazard potential and fair condition, ongoing monitoring and maintenance efforts are essential to ensure the safety and longevity of the dam for both recreational and environmental purposes in the years to come.

Year Completed

1965

Dam Length

320

Dam Height

11

River Or Stream

Abbott Drain

Primary Dam Type

Earth

Surface Area

285

Hydraulic Height

9.3

Drainage Area

4.5

Nid Storage

1455

Structural Height

11

Hazard Potential

Low

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.