Happy Hollow Lake Dam
Happy Hollow Lake Dam is an earth dam located in Knox County, Illinois, built in 1940. It carries a Significant hazard potential classification.
About Happy Hollow Lake Dam
The primary purpose of Happy Hollow Lake Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Happy Hollow Lake Association (private). It impounds the Trib Spoon River near Dahinda.
The dam stands 52 feet tall and stretches 260 feet across, and has a maximum storage capacity of 232 acre-feet. Completed in 1940, the structure is well-established, with more than 75 years of service.
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. The most recent inspection on record was 03/28/2024.
At 52 feet, this dam is taller than 93% of dams nationwide.
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Location
| State | Illinois |
| County | Knox |
| Nearest City | Dahinda |
| River/Stream | Trib Spoon River |
| Coordinates | 40.92681, -90.07401 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 52 ft |
| Dam Height | 52 ft |
| Dam Length | 260 ft |
| Year Completed | 1940 (86 years old) |
Storage & Hydraulics
| NID Storage | 232 acre-ft |
| Max Storage | 232 acre-ft |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | HAPPY HOLLOW LAKE ASSOCIATION |
| Owner Type | Private |
| Hazard Classification | Significant |
| Condition Assessment | Not Available |
| Last Inspection | 03/28/2024 |
| Emergency Action Plan | No |
Identifiers
| NID ID | IL00417 |
| Federal ID | IL00417 |
| More Info | State Dam Safety Program |