Gridley Dam Reservoir Report
Nearby: Prairie Lake Dam Drake Lake Dam
Last Updated: December 21, 2025
Gridley Dam, located in Chandlerville, Illinois, is a state-owned structure designed by the Illinois Department of Natural Resources.
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Summary
Completed in 1998, this earth dam serves a primary purpose of recreation, providing a serene reservoir with a surface area of 24.6 acres and a maximum storage capacity of 475 acre-feet. Situated on the tributary of Panther Creek, the dam stands at a height of 51 feet and stretches 414 feet in length, offering visitors a tranquil setting for outdoor activities like fishing, boating, and picnicking.
Despite its low hazard potential, Gridley Dam is subject to state regulation, inspection, and enforcement by the Illinois Department of Natural Resources. With a moderate risk assessment rating of 3, the dam's condition assessment and emergency preparedness details are currently unavailable. The spillway, with a width of 120 feet, is uncontrolled, and the outlet gates function in a similar manner. Although the dam has not been modified in recent years, regular inspections are conducted every five years to ensure its safety and structural integrity.
Gridley Dam's location in Cass County, Illinois, under the jurisdiction of the St. Louis District, offers a peaceful recreational retreat for water resource and climate enthusiasts. The dam's strategic position on the tributary of Panther Creek provides a vital source of water storage for the surrounding area, with a drainage area of 0.33 square miles. Visitors can enjoy the natural beauty of the reservoir while appreciating the dam's role in water conservation and leisure activities.
Year Completed |
1998 |
Dam Length |
414 |
Dam Height |
51 |
River Or Stream |
TRIB PANTHER CREEK |
Primary Dam Type |
Earth |
Surface Area |
24.6 |
Drainage Area |
0.33 |
Nid Storage |
475 |
Outlet Gates |
Uncontrolled |
Hazard Potential |
Low |
Foundations |
Unlisted/Unknown |
Nid Height |
51 |
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.
Gridley Dam