Hidden Valley Lake Dam Reservoir Report

Last Updated: December 13, 2025

Hidden Valley Lake Dam, located in Ogle, Illinois, is a privately-owned earth dam completed in 1968 for recreational purposes.


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Summary

Standing at a height of 16 feet and a length of 505 feet, the dam has a storage capacity of 256 acre-feet and serves as a popular spot for outdoor activities in the area. With a significant hazard potential and moderate risk assessment, the dam is state-regulated by the Illinois Department of Natural Resources, ensuring regular inspections and enforcement measures are in place to maintain its integrity and safety.

Situated on the Tributary of Stillman Creek, Hidden Valley Lake Dam has an uncontrolled spillway with a width of 95 feet and a maximum discharge capacity of 2116 cubic feet per second. Despite its buttress core type and unknown foundation, the dam has not been modified in recent years and lacks detailed condition assessment data. While the Emergency Action Plan was last revised in 2015 and meets guidelines, the risk management measures and inundation maps are not readily available. Overall, Hidden Valley Lake Dam offers a picturesque setting for recreation but requires ongoing monitoring and maintenance to mitigate potential risks and ensure public safety in the event of emergencies.

Year Completed

1968

Dam Length

505

Dam Height

16

River Or Stream

TRIB STILLMAN CREEK

Primary Dam Type

Earth

Surface Area

19

Drainage Area

2.5

Nid Storage

256

Outlet Gates

Uncontrolled

Hazard Potential

Significant

Foundations

Unlisted/Unknown

Nid Height

16
       
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.
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Area Campgrounds