Stonehenge Lake Dam is an earth dam located in St. Clair County, Illinois, built in 2008. It carries a Significant hazard potential classification.
Dam profile
NID height · 33 ft33 ft tall and 320 ft long, taller than 76% of U.S. dams with a recorded height. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic embankment section and the water level is illustrative.
About Stonehenge Lake Dam
The primary purpose of Stonehenge Lake Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Stonehenge Land Trust II (private). It impounds the Prairie Du Long Creek near Waterloo.
The dam stands 33 feet tall and stretches 320 feet across, creates a reservoir covering 18 acres, has a maximum storage capacity of 200 acre-feet, and collects water from a drainage area of 4 square miles. Completed in 2008, the structure is relatively new.
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 12/02/2021.
At 33 feet, this dam is taller than 76% of dams nationwide.
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Location
| State | Illinois |
| County | St. Clair |
| Nearest City | Waterloo |
| River/Stream | Prairie Du Long Creek |
| Coordinates | 38.39835, -90.12496 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 33 ft |
| Dam Height | 33 ft |
| Dam Length | 320 ft |
| Year Completed | 2008 (18 years old) |
Storage & Hydraulics
| NID Storage | 200 acre-ft |
| Max Storage | 200 acre-ft |
| Normal Storage | 95 acre-ft |
| Surface Area | 18 acres |
| Drainage Area | 4 sq mi |
| Max Discharge | 2,846 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | Stonehenge Land Trust II |
| Owner Type | Private |
| Hazard Classification | Significant |
| Condition Assessment | Not assessed |
| Last Inspection | 12/02/2021 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | IL50575 |
| Federal ID | IL50575 |
| More Info | State Dam Safety Program |