Irwin Lake Dam
Irwin Lake Dam is an earth dam located in Mercer County, Illinois, built in 1965. It carries a Low hazard potential classification.
About Irwin Lake Dam
The primary purpose of Irwin Lake Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Marie Irwin (private). It impounds the Trib Edwards River near Aledo-offstream.
The dam stands 34 feet tall and stretches 430 feet across, and has a maximum storage capacity of 125 acre-feet. Completed in 1965, the structure is well into its service life at over 50 years old.
This dam has a low hazard potential classification, meaning that failure would cause minimal damage, limited primarily to the dam owner's property, with no expected loss of life. The most recent inspection on record was 05/02/2025.
At 34 feet, this dam is taller than 80% of dams nationwide.
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Location
| State | Illinois |
| County | Mercer |
| Nearest City | Aledo-offstream |
| River/Stream | Trib Edwards River |
| Coordinates | 41.21437, -90.74444 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 34 ft |
| Dam Height | 34 ft |
| Dam Length | 430 ft |
| Year Completed | 1965 (61 years old) |
Storage & Hydraulics
| NID Storage | 125 acre-ft |
| Max Storage | 125 acre-ft |
| Normal Storage | 87 acre-ft |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | MARIE IRWIN |
| Owner Type | Private |
| Hazard Classification | Low |
| Condition Assessment | Not Available |
| Last Inspection | 05/02/2025 |
| Emergency Action Plan | No |
Identifiers
| NID ID | IL01201 |
| Federal ID | IL01201 |
| More Info | State Dam Safety Program |