Twin Lakes Dam Reservoir Report

Last Updated: December 6, 2025

Twin Lakes Dam, located in Mascoutah, Illinois, is a private-owned structure primarily used for recreation.


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Summary

Built in 1949 by designer B. Neunaber, this earth dam stands at a height of 28 feet and stretches 310 feet in length, with a storage capacity of 140 acre-feet. The dam is regulated and inspected by the Illinois Department of Natural Resources, ensuring its safety and compliance with state regulations.

Despite its low hazard potential, Twin Lakes Dam poses a moderate risk, as assessed by authorities. The spillway, with a width of 15 feet, is uncontrolled, and the outlet gates operate in the same manner. While the structure has not undergone recent condition assessments, inspections are carried out every five years to ensure its integrity and functionality. The surrounding area is monitored for any potential risks, with emergency protocols in place to mitigate any potential hazards.

Water resource and climate enthusiasts will find Twin Lakes Dam to be an intriguing example of a privately-owned recreational dam in Illinois. With a rich history dating back to its construction in 1949, this structure provides both leisure opportunities for visitors and essential water management functions. While considered to have a low hazard potential, the dam is subject to regular inspections and risk assessments to maintain its safety standards and protect the surrounding community from any potential risks.

Year Completed

1949

Dam Length

310

Dam Height

28

River Or Stream

TRIB WENDELL BRANCH

Primary Dam Type

Earth

Nid Storage

140

Outlet Gates

Uncontrolled

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

28
       
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.