Lake Petersburg Dam Reservoir Report
Nearby: Browns Lake Dam Country Lake Dam
Last Updated: December 21, 2025
Lake Petersburg Dam, located in Menard, Illinois, is a privately owned structure that serves as a recreational spot for water enthusiasts.
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Summary
Completed in 1961, this earth dam stands at a height of 85 feet and has a length of 1300 feet, providing a storage capacity of 6703 acre-feet. The dam overlooks the Tributary of the Sangamon River, offering a picturesque setting for visitors to enjoy various water activities.
Managed by the Illinois Department of Natural Resources, the dam is classified as having a high hazard potential due to its location and structural characteristics. The spillway, with a width of 85 feet, is uncontrolled, and the outlet gates are also uncontrolled. Despite its age, the dam has undergone regular inspections, with the last one conducted in September 2020. The emergency action plan has been updated as recently as February 2021, ensuring the safety of surrounding communities in the event of a potential breach.
With a moderate risk assessment rating of 3, Lake Petersburg Dam continues to stand as a crucial water resource in the region. As climate change impacts water resources, maintaining and monitoring the dam's condition is essential to ensure its continued functionality and safety. Water and climate enthusiasts can appreciate the beauty and importance of Lake Petersburg Dam while recognizing the ongoing efforts to manage and protect this vital infrastructure.
Year Completed |
1961 |
Dam Length |
1300 |
Dam Height |
85 |
River Or Stream |
TRIB SANGAMON RIVER |
Primary Dam Type |
Earth |
Nid Storage |
6703 |
Outlet Gates |
Uncontrolled |
Hazard Potential |
High |
Foundations |
Unlisted/Unknown |
Nid Height |
85 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Sangamon River At Petersburg
|
209cfs |
Salt Creek Near Greenview
|
204cfs |
Sangamon River Near Oakford
|
421cfs |
Spring Creek At Springfield
|
7cfs |
Sangamon River At Riverton
|
125cfs |
South Fork Sangamon River Nr Rochester
|
11cfs |
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.
Lake Petersburg Dam