Amoskeag
Amoskeag is a concrete dam located in Hillsborough, New Hampshire, built in 1921. It carries a High hazard potential classification and has a fair condition assessment.
About Amoskeag
The primary purpose of Amoskeag is hydroelectric. The dam generates hydroelectric power by channeling water through turbines, converting the energy of flowing water into electricity. It impounds the Merrimack River near Manchester.
The dam stands 29 feet tall and stretches 1,075 feet across, creates a reservoir covering 478 acres, has a maximum storage capacity of 4,320 acre-feet, and collects water from a drainage area of 2,854 square miles. Completed in 1921, 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 fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. An emergency action plan is in place for this dam. The most recent inspection on record was 08/06/2025.
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 | Hillsborough |
| Nearest City | Manchester |
| River/Stream | Merrimack River |
| Coordinates | 43.00220, -71.47230 |
Physical Characteristics
| Dam Type | Concrete |
| NID Height | 29 ft |
| Dam Height | 29 ft |
| Dam Length | 1,075 ft |
| Year Completed | 1921 (105 years old) |
Storage & Hydraulics
| NID Storage | 4,320 acre-ft |
| Max Storage | 4,320 acre-ft |
| Normal Storage | 4,320 acre-ft |
| Surface Area | 478 acres |
| Drainage Area | 2,854 sq mi |
| Max Discharge | 87,000 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner Type | Not Listed |
| Hazard Classification | High |
| Condition Assessment | Fair |
| Last Inspection | 08/06/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NH00102 |
| Federal ID | NH00102 |
| More Info | State Dam Safety Program |