Grand Lake St. Marys - West Embankment is an earth dam located in Mercer County, Ohio, built in 1841. It carries a High hazard potential classification and has a poor condition assessment.
Dam profile
NID height · 20 ft20 ft tall and 9,760 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 Grand Lake St. Marys - West Embankment
The primary purpose of Grand Lake St. Marys - West Embankment is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Odnr, Division of Parks & Watercraft (state). It impounds the Beaver Creek near Celina.
The dam stands 20 feet tall and stretches 9,760 feet across, creates a reservoir covering 13,981 acres, has a maximum storage capacity of 156,383 acre-feet, and collects water from a drainage area of 110 square miles. Completed in 1841, the structure is one of the older dams in the region, with over a century and a half of service.
This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated poor, meaning the dam has recognized safety deficiencies that require remediation to address risks. An emergency action plan is in place for this dam. The most recent inspection on record was 11/20/2024.
Living Downstream
If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Ohio dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Ohio |
| County | Mercer |
| Nearest City | Celina |
| River/Stream | Beaver Creek |
| Coordinates | 40.53500, -84.57333 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 20 ft |
| Dam Height | 20 ft |
| Dam Length | 9,760 ft |
| Year Completed | 1841 (185 years old) |
Storage & Hydraulics
| NID Storage | 156,383 acre-ft |
| Max Storage | 156,383 acre-ft |
| Normal Storage | 62,914 acre-ft |
| Surface Area | 13,981 acres |
| Drainage Area | 110 sq mi |
| Max Discharge | 18,000 cfs |
Ownership & Safety
| Purpose | Recreation |
| Owner | Odnr, Division of Parks & Watercraft |
| Owner Type | State |
| Hazard Classification | High |
| Condition Assessment | Poor |
| Last Inspection | 11/20/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | OH00580 |
| Federal ID | OH00580 |
| More Info | State Dam Safety Program |