Little Cache Structure 8 Dam Reservoir Report

Last Updated: December 5, 2025

Little Cache Structure 8 Dam, located in Johnson, Illinois, was completed in 1970 and is owned by the local government.


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Summary

Designed by USDA NRCS, this earth dam stands at a height of 21 feet and has a length of 820 feet. Its primary purpose is flood risk reduction, with a storage capacity of 242 acre-feet and a maximum discharge of 1692 cubic feet per second.

Managed by the Illinois Department of Natural Resources, the dam is regulated, permitted, inspected, and enforced by the state. With a significant hazard potential and a moderate risk assessment score of 3, the dam is deemed to meet guidelines for emergency action plans. Although the condition assessment is not available, the dam has undergone inspections every three years, with the last one conducted in November 2020. The spillway type is uncontrolled, with a width of 95 feet, and the outlet gates are also uncontrolled.

Little Cache Structure 8 Dam not only serves as a vital flood control structure but also provides opportunities for recreation. With its strategic location on the TRIB Little Cache Creek, this dam plays a crucial role in managing water resources in the area. For water resource and climate enthusiasts, the dam's design, operational details, and regulatory oversight make it an intriguing case study in sustainable water management practices.

Year Completed

1970

Dam Length

820

Dam Height

21

River Or Stream

TRIB LITTLE CACHE CREEK

Primary Dam Type

Earth

Nid Storage

242

Outlet Gates

Uncontrolled

Hazard Potential

Significant

Foundations

Unlisted/Unknown

Nid Height

21
       
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.