Lake Piasa Dam is an earth dam located in Jersey County, Illinois, built in 1963. It carries a Low hazard potential classification.
Dam profile
NID height · 47 ft47 ft tall and 515 ft long, taller than 91% of U.S. dams with a recorded height. Height is drawn to scale against a ten-story building, about 100 ft; the profile is a generic embankment section and the water level is illustrative.
About Lake Piasa Dam
The primary purpose of Lake Piasa Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Lake Piasa Board of Trustees (local government). It impounds the Little Piasa Creek-offstream near Alton.
The dam stands 47 feet tall and stretches 515 feet across, and has a maximum storage capacity of 292 acre-feet. Completed in 1963, the structure is well into its service life at over 50 years old.
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 08/27/2025.
At 47 feet, this dam is taller than 91% of dams nationwide.
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Location
| State | Illinois |
| County | Jersey |
| Nearest City | Alton |
| River/Stream | Little Piasa Creek-offstream |
| Coordinates | 39.02031, -90.19505 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 47 ft |
| Dam Height | 47 ft |
| Dam Length | 515 ft |
| Year Completed | 1963 (63 years old) |
Storage & Hydraulics
| NID Storage | 292 acre-ft |
| Max Storage | 292 acre-ft |
| Normal Storage | 235 acre-ft |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | Lake Piasa Board of Trustees |
| Owner Type | Local Government |
| Hazard Classification | Low |
| Condition Assessment | Not assessed |
| Last Inspection | 08/27/2025 |
| Emergency Action Plan | No |
Identifiers
| NID ID | IL00667 |
| Federal ID | IL00667 |
| More Info | State Dam Safety Program |