Mascoma Lake Dam
Mascoma Lake Dam is a concrete dam located in Grafton County, New Hampshire, built in 1881. It carries a High hazard potential classification and has a poor condition assessment.
About Mascoma Lake Dam
The primary purpose of Mascoma Lake Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Nh Des Water Division (state). It impounds the Mascoma River near Lebanon.
The dam stands 18 feet tall and stretches 575 feet across, creates a reservoir covering 1,155 acres, has a maximum storage capacity of 18,300 acre-feet, and collects water from a drainage area of 153 square miles. Completed in 1881, 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 10/31/2022.
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 | 43.64830, -72.18220 |
Physical Characteristics
| Dam Type | Concrete |
| NID Height | 18 ft |
| Dam Height | 18 ft |
| Dam Length | 575 ft |
| Year Completed | 1881 (145 years old) |
Storage & Hydraulics
| NID Storage | 18,300 acre-ft |
| Max Storage | 18,300 acre-ft |
| Normal Storage | 8,332 acre-ft |
| Surface Area | 1,155 acres |
| Drainage Area | 153 sq mi |
| Max Discharge | 17,255 cfs |
Ownership & Safety
| Purpose | Recreation |
| Owner | NH DES WATER DIVISION |
| Owner Type | State |
| Hazard Classification | High |
| Condition Assessment | Poor |
| Last Inspection | 10/31/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NH00153 |
| Federal ID | NH00153 |
| More Info | State Dam Safety Program |