Cedar Lake Dam Reservoir Report

Last Updated: December 6, 2025

Located in Rattlesnake Ferry, Illinois, Cedar Lake Dam stands as a vital water resource and recreational hub for the local community.


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Summary

Constructed in 1974 by Stanley Consultants, this earth dam spans 1690 feet and reaches a height of 74 feet, providing a storage capacity of 49,336 acre-feet. The dam, situated on Cedar Creek, serves dual purposes of recreation and water supply, boasting a surface area of 1750 acres and a drainage area of 30.2 square miles.

With a high hazard potential and a moderate risk assessment rating, Cedar Lake Dam is regulated by the Illinois Department of Natural Resources (IDNR) and undergoes regular state inspections and enforcement measures. The dam features an uncontrolled spillway and outlet gates, with a maximum discharge capacity of 10,234 cubic feet per second. Despite its age, the dam's condition assessment is not available, emphasizing the need for continued monitoring and maintenance to ensure its structural integrity and safety for the surrounding community.

As a focal point for outdoor activities and water recreation, Cedar Lake Dam offers a scenic backdrop for visitors to enjoy boating, fishing, and other leisure pursuits. With its significant storage capacity and strategic location within Jackson County, Illinois, the dam plays a crucial role in providing water resources for the region while also serving as a popular destination for nature enthusiasts and climate advocates alike.

Year Completed

1974

Dam Length

1690

Dam Height

74

River Or Stream

CEDAR CREEK

Primary Dam Type

Earth

Surface Area

1750

Drainage Area

30.2

Nid Storage

49336

Outlet Gates

Uncontrolled

Hazard Potential

High

Foundations

Unlisted/Unknown

Nid Height

74
       
Seasonal Comparison

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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.