Otter Lake Dam
Otter Lake Dam is an earth dam located in Macoupin County, Illinois, built in 1969. It carries a Significant hazard potential classification.
About Otter Lake Dam
The primary purpose of Otter Lake Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Otter Lake Water Commission (public utility). It impounds the West Fork Otter Creek near Rockridge.
The dam stands 71 feet tall and stretches 1,010 feet across, creates a reservoir covering 760 acres, has a maximum storage capacity of 24,708 acre-feet, and collects water from a drainage area of 20 square miles. Completed in 1969, 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 04/26/2023.
At 71 feet, this dam is taller than 96% of all dams in the United States.
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Location
| State | Illinois |
| County | Macoupin |
| Nearest City | Rockridge |
| River/Stream | West Fork Otter Creek |
| Coordinates | 39.40715, -89.91006 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 71 ft |
| Dam Height | 71 ft |
| Dam Length | 1,010 ft |
| Year Completed | 1969 (57 years old) |
Storage & Hydraulics
| NID Storage | 24,708 acre-ft |
| Max Storage | 24,708 acre-ft |
| Normal Storage | 15,563 acre-ft |
| Surface Area | 760 acres |
| Drainage Area | 20 sq mi |
| Max Discharge | 21,153 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | OTTER LAKE WATER COMMISSION |
| Owner Type | Public Utility |
| Hazard Classification | Significant |
| Condition Assessment | Not Available |
| Last Inspection | 04/26/2023 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | IL00133 |
| Federal ID | IL00133 |
| More Info | State Dam Safety Program |