Twin Lakes Dam is an earth dam located in Madison County, Illinois, built in 1949. It carries a Low hazard potential classification.
Dam profile
NID height · 28 ft28 ft tall and 310 ft long, taller than 62% 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 Twin Lakes Dam
The primary purpose of Twin Lakes Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Twin Lakes Association (private). It impounds the Trib Wendell Branch near Mascoutah.
The dam stands 28 feet tall and stretches 310 feet across, and has a maximum storage capacity of 140 acre-feet. Completed in 1949, the structure is well-established, with more than 75 years of service.
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 07/11/2025.
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Location
| State | Illinois |
| County | Madison |
| Nearest City | Mascoutah |
| River/Stream | Trib Wendell Branch |
| Coordinates | 38.72778, -89.86491 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 28 ft |
| Dam Height | 28 ft |
| Dam Length | 310 ft |
| Year Completed | 1949 (77 years old) |
Storage & Hydraulics
| NID Storage | 140 acre-ft |
| Max Storage | 140 acre-ft |
| Normal Storage | 111 acre-ft |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | Twin Lakes Association |
| Owner Type | Private |
| Hazard Classification | Low |
| Condition Assessment | Not assessed |
| Last Inspection | 07/11/2025 |
| Emergency Action Plan | No |
Identifiers
| NID ID | IL00194 |
| Federal ID | IL00194 |
| More Info | State Dam Safety Program |