St. Marys Lime Sludge Lagoons is an earth dam located in Auglaize County, Ohio, built in 1988. It carries a Significant hazard potential classification and has a satisfactory condition assessment.
Dam profile
NID height · 13 ft13 ft tall and 2,640 ft long. 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 St. Marys Lime Sludge Lagoons
The primary purpose of St. Marys Lime Sludge Lagoons 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 City of St. Marys (local government). It impounds the Koop near St. Marys.
The dam stands 13 feet tall and stretches 2,640 feet across, creates a reservoir covering 12 acres, has a maximum storage capacity of 128 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 12/04/2024.
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Location
| State | Ohio |
| County | Auglaize |
| Nearest City | St. Marys |
| River/Stream | Koop |
| Coordinates | 40.51500, -84.38500 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 13 ft |
| Dam Height | 13 ft |
| Dam Length | 2,640 ft |
| Year Completed | 1988 (38 years old) |
Storage & Hydraulics
| NID Storage | 128 acre-ft |
| Max Storage | 128 acre-ft |
| Normal Storage | 92 acre-ft |
| Surface Area | 12 acres |
| Drainage Area | 0 sq mi |
| Max Discharge | 10 cfs |
Ownership & Safety
| Purpose | Tailings |
| Owner | City of St. Marys |
| Owner Type | Local Government |
| Hazard Classification | Significant |
| Condition Assessment | Satisfactory |
| Last Inspection | 12/04/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | OH01212 |
| Federal ID | OH01212 |
| More Info | State Dam Safety Program |