Stephen A. Forbes State Park Lake Dam is an earth dam located in Marion County, Illinois, built in 1963. It carries a Significant hazard potential classification.
Dam profile
NID height · 46 ft46 ft tall and 1,335 ft long, taller than 91% of U.S. dams with a recorded height. Height is drawn to scale against a ten-story building, about 100 ft; the profile is a generic embankment section and the water level is illustrative.
About Stephen A. Forbes State Park Lake Dam
The primary purpose of Stephen A. Forbes State Park Lake Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Illinois Department of Natural Resources (state). It impounds the Lost Fork Creek near Wayne City.
The dam stands 46 feet tall and stretches 1,335 feet across, creates a reservoir covering 585 acres, has a maximum storage capacity of 15,739 acre-feet, and collects water from a drainage area of 21 square miles. Completed in 1963, the structure is well into its service life at over 50 years old.
This dam has a significant hazard potential classification, meaning that a failure could cause significant economic damage — flooding roads, bridges, or property downstream — but is not expected to result in loss of life. An emergency action plan is in place for this dam. The most recent inspection on record was 11/25/2024.
At 46 feet, this dam is taller than 91% of dams nationwide.
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Location
| State | Illinois |
| County | Marion |
| Nearest City | Wayne City |
| River/Stream | Lost Fork Creek |
| Coordinates | 38.71302, -88.74679 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 46 ft |
| Dam Height | 46 ft |
| Dam Length | 1,335 ft |
| Year Completed | 1963 (63 years old) |
Storage & Hydraulics
| NID Storage | 15,739 acre-ft |
| Max Storage | 15,739 acre-ft |
| Normal Storage | 8,800 acre-ft |
| Surface Area | 585 acres |
| Drainage Area | 21 sq mi |
| Max Discharge | 30,848 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | Illinois Department of Natural Resources |
| Owner Type | State |
| Hazard Classification | Significant |
| Condition Assessment | Not assessed |
| Last Inspection | 11/25/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | IL00230 |
| Federal ID | IL00230 |
| More Info | State Dam Safety Program |