Old Gillespie Lake Dam is an earth dam located in Macoupin County, Illinois, built in 1923. It carries a Low hazard potential classification.
Dam profile
NID height · 35 ft35 ft tall and 335 ft long, taller than 80% 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 Old Gillespie Lake Dam
The primary purpose of Old Gillespie Lake Dam is water supply. The dam stores water for municipal, industrial, or agricultural use, helping ensure a reliable supply for the surrounding area. The dam is owned by City of Gillespie (local government). It impounds the Dry Fork near Hardin.
The dam stands 35 feet tall and stretches 335 feet across, creates a reservoir covering 71 acres, has a maximum storage capacity of 1,149 acre-feet, and collects water from a drainage area of 5 square miles. Completed in 1923, the structure is over a century 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 08/02/2024.
At 35 feet, this dam is taller than 80% of dams nationwide.
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Location
| State | Illinois |
| County | Macoupin |
| Nearest City | Hardin |
| River/Stream | Dry Fork |
| Coordinates | 39.14678, -89.86361 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 35 ft |
| Dam Height | 35 ft |
| Dam Length | 335 ft |
| Year Completed | 1923 (103 years old) |
Storage & Hydraulics
| NID Storage | 1,149 acre-ft |
| Max Storage | 1,149 acre-ft |
| Normal Storage | 592 acre-ft |
| Surface Area | 71 acres |
| Drainage Area | 5 sq mi |
| Max Discharge | 3,598 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Water Supply |
| Owner | City of Gillespie |
| Owner Type | Local Government |
| Hazard Classification | Low |
| Condition Assessment | Not assessed |
| Last Inspection | 08/02/2024 |
| Emergency Action Plan | No |
Identifiers
| NID ID | IL00777 |
| Federal ID | IL00777 |
| More Info | State Dam Safety Program |