St. Henry Wwt Lagoon
St. Henry Wwt Lagoon is an earth dam located in Mercer County, Ohio, built in 1988. It carries a Significant hazard potential classification and has a satisfactory condition assessment.
About St. Henry Wwt Lagoon
The primary purpose of St. Henry Wwt Lagoon is tailings. Tailings dams contain waste material from mining operations — typically a slurry of finely ground rock left over after valuable minerals have been extracted. These structures require ongoing monitoring because tailings can contain heavy metals and other contaminants. The dam is owned by Village Of St. Henry (local government). It impounds the Coldwater Creek - Offstream near Coldwater.
The dam stands 27 feet tall and stretches 5,540 feet across, creates a reservoir covering 45 acres, has a maximum storage capacity of 501 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1988, the structure is 38 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. Its condition is rated satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 11/07/2024.
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Location
| State | Ohio |
| County | Mercer |
| Nearest City | Coldwater |
| River/Stream | Coldwater Creek - Offstream |
| Coordinates | 40.43000, -84.62444 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 27 ft |
| Dam Height | 27 ft |
| Dam Length | 5,540 ft |
| Year Completed | 1988 (38 years old) |
Storage & Hydraulics
| NID Storage | 501 acre-ft |
| Max Storage | 501 acre-ft |
| Normal Storage | 395 acre-ft |
| Surface Area | 45 acres |
| Drainage Area | 0 sq mi |
| Max Discharge | 20 cfs |
Ownership & Safety
| Purpose | Tailings |
| Owner | Village of St. Henry |
| Owner Type | Local Government |
| Hazard Classification | Significant |
| Condition Assessment | Satisfactory |
| Last Inspection | 11/07/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | OH02727 |
| Federal ID | OH02727 |
| More Info | State Dam Safety Program |