New Gillespie Lake Dam is an earth dam located in Macoupin County, Illinois, built in 1956. It carries a Significant hazard potential classification.
Dam profile
NID height · 41 ft41 ft tall and 868 ft long, taller than 87% 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 New Gillespie Lake Dam
The primary purpose of New 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 Macoupin Creek near Macoupin Station.
The dam stands 41 feet tall and stretches 868 feet across, creates a reservoir covering 216 acres, has a maximum storage capacity of 4,975 acre-feet, and collects water from a drainage area of 12 square miles. Completed in 1956, the structure is well into its service life at over 50 years old.
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 08/12/2023.
At 41 feet, this dam is taller than 87% of dams nationwide.
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Location
| State | Illinois |
| County | Macoupin |
| Nearest City | Macoupin Station |
| River/Stream | Dry Fork Macoupin Creek |
| Coordinates | 39.14528, -89.88889 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 41 ft |
| Dam Height | 41 ft |
| Dam Length | 868 ft |
| Year Completed | 1956 (70 years old) |
Storage & Hydraulics
| NID Storage | 4,975 acre-ft |
| Max Storage | 4,975 acre-ft |
| Normal Storage | 2,325 acre-ft |
| Surface Area | 216 acres |
| Drainage Area | 12 sq mi |
| Max Discharge | 12,283 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Water Supply |
| Owner | City of Gillespie |
| Owner Type | Local Government |
| Hazard Classification | Significant |
| Condition Assessment | Not assessed |
| Last Inspection | 08/12/2023 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | IL00781 |
| Federal ID | IL00781 |
| More Info | State Dam Safety Program |