Prairie Lake Dam Reservoir Report
Nearby: Drake Lake Dam Gridley Dam
Last Updated: December 21, 2025
Prairie Lake Dam, also known as Site M, is a state-owned structure located in Chandlerville, Illinois.
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Summary
Built in 1999 by Hanson Engineers, this earth dam stands at a height of 68 feet and spans 820 feet across the tributary of Cox Creek. With a primary purpose of recreation, the dam provides a surface area of 210 acres and a maximum storage capacity of 6085 acre-feet, making it a popular destination for water enthusiasts in Cass County.
Managed by the Illinois Department of Natural Resources (IDNR), Prairie Lake Dam is regulated, inspected, and permitted by the state authorities to ensure its safety and compliance with environmental standards. The dam's spillway, with a width of 359 feet, is uncontrolled, posing a high hazard potential in case of emergencies. Despite its moderate risk assessment, the dam lacks a detailed condition assessment and an Emergency Action Plan (EAP), raising concerns about its long-term management and safety protocols.
For water resource and climate enthusiasts, Prairie Lake Dam offers a captivating insight into the intricate balance between recreation, water management, and environmental conservation. Its strategic location, impressive dimensions, and regulatory oversight by the state highlight the importance of sustainable dam infrastructure in supporting various recreational activities while safeguarding the surrounding ecosystem. As efforts continue to improve the dam's risk management measures and emergency preparedness, Prairie Lake remains a significant landmark in Illinois's water infrastructure landscape.
Year Completed |
1999 |
Dam Length |
820 |
Dam Height |
68 |
River Or Stream |
TRIB COX CREEK |
Primary Dam Type |
Earth |
Surface Area |
210 |
Drainage Area |
3.4 |
Nid Storage |
6085 |
Outlet Gates |
Uncontrolled |
Hazard Potential |
High |
Foundations |
Unlisted/Unknown |
Nid Height |
68 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Sangamon River Near Oakford
|
582cfs |
Sangamon River At Petersburg
|
199cfs |
Salt Creek Near Greenview
|
232cfs |
Spring Creek At Springfield
|
6cfs |
Sangamon River At Riverton
|
188cfs |
La Moine River At Ripley
|
23cfs |
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.
Prairie Lake Dam