Coffeen Southwest Detention Pond Dam
Coffeen Southwest Detention Pond Dam is an earth dam located in Montgomery County, Illinois, built in 2010. It carries a Low hazard potential classification.
About Coffeen Southwest Detention Pond Dam
The primary purpose of Coffeen Southwest Detention Pond Dam is flood risk reduction. The dam is designed to control downstream flooding by temporarily storing excess water during storms and releasing it at a controlled rate. The dam is owned by Dynegy Midwest Generation, Inc. (public utility). It impounds the Trib Mcdavid Branch near Greenville.
The dam stands 23 feet tall and stretches 350 feet across, creates a reservoir covering 4 acres, has a maximum storage capacity of 86 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 2010, the structure is relatively new.
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 09/17/2025.
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Location
| State | Illinois |
| County | Montgomery |
| Nearest City | Greenville |
| River/Stream | Trib Mcdavid Branch |
| Coordinates | 39.06701, -89.40348 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 23 ft |
| Dam Height | 23 ft |
| Dam Length | 350 ft |
| Year Completed | 2010 (16 years old) |
Storage & Hydraulics
| NID Storage | 86 acre-ft |
| Max Storage | 86 acre-ft |
| Normal Storage | 42 acre-ft |
| Surface Area | 4 acres |
| Drainage Area | 0 sq mi |
| Max Discharge | 84 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | DYNEGY MIDWEST GENERATION, INC. |
| Owner Type | Public Utility |
| Hazard Classification | Low |
| Condition Assessment | Not Available |
| Last Inspection | 09/17/2025 |
| Emergency Action Plan | No |
Identifiers
| NID ID | IL50582 |
| Federal ID | IL50582 |
| More Info | State Dam Safety Program |