Lake Hillsboro Dam Reservoir Report
Last Updated: December 6, 2025
Lake Hillsboro Dam, located in Montgomery, Illinois, was completed in 1917 and stands at a height of 34 feet, with a length of 693 feet.
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Summary
This Earth dam, primarily serving recreational purposes, holds a storage capacity of 1747 acre-feet and covers a surface area of 107 acres. The dam regulates water from the Trib Middle Fork Shoal Creek, with a maximum discharge rate of 3276 cubic feet per second.
Managed by the local government, the dam is state-regulated by the Illinois Department of Natural Resources (IDNR), with regular inspections and enforcement in place. Despite its significant hazard potential, the dam is currently assessed as having an unknown condition. The spillway, measuring 93 feet in width, is uncontrolled, and the outlet gates operate similarly.
Lake Hillsboro Dam's risk assessment is rated as moderate, with a risk level of 3. While the Emergency Action Plan (EAP) status and risk management measures are not available, the dam continues to play a crucial role in water supply and recreation for the surrounding area, showcasing the intersection of water resource management and climate resilience efforts.
Year Completed |
1917 |
Dam Length |
693 |
Dam Height |
34 |
River Or Stream |
TRIB MIDDLE FORK SHOAL CREEK |
Primary Dam Type |
Earth |
Surface Area |
107 |
Drainage Area |
6.8 |
Nid Storage |
1747 |
Outlet Gates |
Uncontrolled |
Hazard Potential |
Significant |
Foundations |
Unlisted/Unknown |
Nid Height |
34 |
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.
Lake Hillsboro Dam