Lagg Lake 1 Dam Reservoir Report
Nearby: Lagg Lake 2 Miller Lake Dam
Last Updated: December 6, 2025
Lagg Lake 1 Dam, located in Idlewood, Illinois, is a privately owned earth dam completed in 1976 for the primary purpose of recreation.
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Summary
The dam stands at a height of 18 feet and has a length of 330 feet, with a storage capacity of 88 acre-feet. Situated on TRIB CASEY CREEK, the dam is regulated, permitted, inspected, and enforced by the Illinois Department of Natural Resources. With a low hazard potential and moderate risk assessment, the dam is classified as having a recreational function and is equipped with an uncontrolled spillway system.
Despite its low hazard potential, Lagg Lake 1 Dam is subject to regular inspections with a frequency of every 5 years, with the last inspection conducted in July 2017. The dam is in a condition where assessment is not available, but it meets state guidelines for emergency action plans (EAP) and has not had any recent updates to its EAP or emergency contacts. The risk management measures for the dam are currently not specified, but with its moderate risk assessment, it is crucial for continued monitoring and maintenance to ensure the safety of the structure and surrounding area. For water resource and climate enthusiasts, Lagg Lake 1 Dam presents an interesting case study in private dam ownership and regulation in Illinois.
Year Completed |
1976 |
Dam Length |
330 |
Dam Height |
18 |
River Or Stream |
TRIB CASEY CREEK |
Primary Dam Type |
Earth |
Nid Storage |
88 |
Outlet Gates |
Uncontrolled |
Hazard Potential |
Low |
Foundations |
Unlisted/Unknown |
Nid Height |
18 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Lagg Lake 1 Dam