Rivermill Mascoma Hydro Dam
Rivermill Mascoma Hydro Dam is a concrete dam located in Grafton County, New Hampshire, built in 1920. It carries a High hazard potential classification and has a poor condition assessment.
About Rivermill Mascoma Hydro Dam
The primary purpose of Rivermill Mascoma Hydro Dam is hydroelectric. The dam generates hydroelectric power by channeling water through turbines, converting the energy of flowing water into electricity. The dam is owned by Rivermill Hydroelectric Inc (private). It impounds the Mascoma River near Lebanon.
The dam stands 22 feet tall and stretches 300 feet across, creates a reservoir covering 7 acres, has a maximum storage capacity of 210 acre-feet, and collects water from a drainage area of 188 square miles. Completed in 1920, the structure is over a century 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. An emergency action plan is in place for this dam. The most recent inspection on record was 08/08/2018. That was 7 years ago, which is on the longer end for a high-hazard structure.
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 New Hampshire 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 | New Hampshire |
| County | Grafton |
| Nearest City | Lebanon |
| River/Stream | Mascoma River |
| Coordinates | 43.63840, -72.25720 |
Physical Characteristics
| Dam Type | Concrete |
| NID Height | 22 ft |
| Dam Height | 22 ft |
| Dam Length | 300 ft |
| Year Completed | 1920 (106 years old) |
Storage & Hydraulics
| NID Storage | 210 acre-ft |
| Max Storage | 210 acre-ft |
| Normal Storage | 170 acre-ft |
| Surface Area | 7 acres |
| Drainage Area | 188 sq mi |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner | RIVERMILL HYDROELECTRIC INC |
| Owner Type | Private |
| Hazard Classification | High |
| Condition Assessment | Poor |
| Last Inspection | 08/08/2018 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NH00155 |
| Federal ID | NH00155 |
| More Info | State Dam Safety Program |