Longs Lake Dam Reservoir Report
Nearby: Finger Lake Dam Drake Lake Dam
Last Updated: December 20, 2025
Longs Lake Dam, located in Chandlerville, Illinois, is a private-owned structure built in 1960 primarily for recreation and water supply purposes.
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Summary
Standing at a height of 28 feet and a length of 175 feet, this earth dam with a buttress core serves as a vital resource in the area. The dam's reservoir has a normal storage capacity of 85 acre-feet, providing essential water supply for the community.
Managed by the Illinois Department of Natural Resources, Longs Lake Dam has a low hazard potential and a moderate risk assessment rating. Despite its age, the dam has not undergone recent condition assessments, but regular inspections have been conducted to ensure its structural integrity. The spillway, with a width of 32 feet, is uncontrolled, further emphasizing the importance of proper regulation and maintenance for this critical infrastructure.
With the potential to impact the surrounding area in the event of a failure, Longs Lake Dam's management and maintenance are crucial for safeguarding both the recreational and water supply functions it serves. As climate change continues to impact water resources, the proper regulation and upkeep of structures like Longs Lake Dam are essential in ensuring the safety and sustainability of water supplies in the region.
Year Completed |
1960 |
Dam Length |
175 |
Dam Height |
28 |
River Or Stream |
TRIB PANTHER CREEK |
Primary Dam Type |
Earth |
Nid Storage |
170 |
Outlet Gates |
Uncontrolled |
Hazard Potential |
Low |
Foundations |
Unlisted/Unknown |
Nid Height |
28 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Sangamon River Near Oakford
|
421cfs |
Sangamon River At Petersburg
|
209cfs |
Salt Creek Near Greenview
|
204cfs |
La Moine River At Ripley
|
14cfs |
Spring Creek At Springfield
|
7cfs |
Sangamon River At Riverton
|
125cfs |
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.
Longs Lake Dam