Lake Seneca Dam
Lake Seneca Dam is an earth dam located in Williams County, Ohio, built in 1966. It carries a High hazard potential classification and has a poor condition assessment.
About Lake Seneca Dam
The primary purpose of Lake Seneca Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Lake Seneca Property Owners Assn. (private). It impounds the West Branch St. Joseph River near Montpelier.
The dam stands 36 feet tall and stretches 990 feet across, creates a reservoir covering 233 acres, has a maximum storage capacity of 8,117 acre-feet, and collects water from a drainage area of 106 square miles. Completed in 1966, the structure is well into its service life at over 50 years old.
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. Notably, no emergency action plan is currently on file for this high-hazard dam. The most recent inspection on record was 06/06/2023.
At 36 feet, this dam is taller than 83% of dams nationwide.
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 | Williams |
| Nearest City | Montpelier |
| River/Stream | West Branch St. Joseph River |
| Coordinates | 41.66444, -84.63611 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 36 ft |
| Dam Height | 36 ft |
| Dam Length | 990 ft |
| Year Completed | 1966 (60 years old) |
Storage & Hydraulics
| NID Storage | 8,117 acre-ft |
| Max Storage | 8,117 acre-ft |
| Normal Storage | 1,554 acre-ft |
| Surface Area | 233 acres |
| Drainage Area | 106 sq mi |
| Max Discharge | 92,355 cfs |
Ownership & Safety
| Purpose | Recreation |
| Owner | Lake Seneca Property Owners Assn. |
| Owner Type | Private |
| Hazard Classification | High |
| Condition Assessment | Poor |
| Last Inspection | 06/06/2023 |
| Emergency Action Plan | No |
Identifiers
| NID ID | OH00382 |
| Federal ID | OH00382 |
| More Info | State Dam Safety Program |