Crystal Lake Dam is an earth dam located in St. Clair County, Illinois, built in 1940. It carries a Significant hazard potential classification.
Dam profile
NID height · 18 ft18 ft tall and 140 ft long. 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 Crystal Lake Dam
The primary purpose of Crystal Lake Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Crystal Lake Partners, LLC (private). It impounds the Wolf Branch Creek near Swansea.
The dam stands 18 feet tall and stretches 140 feet across. 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. An emergency action plan is in place for this dam. The most recent inspection on record was 10/24/2024.
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Location
| State | Illinois |
| County | St. Clair |
| Nearest City | Swansea |
| River/Stream | Wolf Branch Creek |
| Coordinates | 38.55952, -89.98428 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 18 ft |
| Dam Height | 18 ft |
| Dam Length | 140 ft |
| Year Completed | 1940 (86 years old) |
Ownership & Safety
| Purpose | Recreation |
| Owner | Crystal Lake Partners, LLC |
| Owner Type | Private |
| Hazard Classification | Significant |
| Condition Assessment | Not assessed |
| Last Inspection | 10/24/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | IL50718 |
| Federal ID | IL50718 |
| More Info | State Dam Safety Program |