Hennepin Station East Ash Pond is an earth dam located in Putnam County, Illinois, built in 1996. It carries a Low hazard potential classification.
Dam profile
NID height · 26 ft26 ft tall and 3,600 ft long, taller than 55% 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 Hennepin Station East Ash Pond
Hennepin Station East Ash Pond is a dam in Putnam, Illinois. The dam is owned by Dynegy Midwest Generation, LLC (public utility). It impounds the Trib Illinois River near Hennepin.
The dam stands 26 feet tall and stretches 3,600 feet across, creates a reservoir covering 16 acres, has a maximum storage capacity of 300 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1996, the structure is 30 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 09/10/2025.
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Location
| State | Illinois |
| County | Putnam |
| Nearest City | Hennepin |
| River/Stream | Trib Illinois River |
| Coordinates | 41.30357, -89.30083 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 26 ft |
| Dam Height | 26 ft |
| Dam Length | 3,600 ft |
| Year Completed | 1996 (30 years old) |
Storage & Hydraulics
| NID Storage | 300 acre-ft |
| Max Storage | 300 acre-ft |
| Normal Storage | 225 acre-ft |
| Surface Area | 16 acres |
| Drainage Area | 0 sq mi |
| Max Discharge | 219 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Other |
| Owner | Dynegy Midwest Generation, LLC |
| Owner Type | Public Utility |
| Hazard Classification | Low |
| Condition Assessment | Not assessed |
| Last Inspection | 09/10/2025 |
| Emergency Action Plan | No |
Identifiers
| NID ID | IL50363 |
| Federal ID | IL50363 |
| More Info | State Dam Safety Program |