Hillsborough Mill
Hillsborough Mill is a concrete dam located in Hillsborough, New Hampshire, built in 1925. It carries a Significant hazard potential classification and has a fair condition assessment.
About Hillsborough Mill
The primary purpose of Hillsborough Mill 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 Eevergreen Electric (private). It impounds the Souhegan River near Wilton.
The dam stands 22 feet tall and stretches 200 feet across, creates a reservoir covering 7 acres, has a maximum storage capacity of 70 acre-feet, and collects water from a drainage area of 97 square miles. Completed in 1925, the structure is over a century old.
This dam has a significant hazard potential classification, meaning that a failure could cause significant economic damage — flooding roads, bridges, or property downstream — but is not expected to result in loss of life. 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 08/25/2022.
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Location
| State | New Hampshire |
| County | Hillsborough |
| Nearest City | Wilton |
| River/Stream | Souhegan River |
| Coordinates | 42.83900, -71.72820 |
Physical Characteristics
| Dam Type | Concrete |
| NID Height | 22 ft |
| Dam Height | 22 ft |
| Dam Length | 200 ft |
| Year Completed | 1925 (101 years old) |
Storage & Hydraulics
| NID Storage | 70 acre-ft |
| Max Storage | 70 acre-ft |
| Normal Storage | 70 acre-ft |
| Surface Area | 7 acres |
| Drainage Area | 97 sq mi |
| Max Discharge | 13,100 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner | EEvergreen Electric |
| Owner Type | Private |
| Hazard Classification | Significant |
| Condition Assessment | Fair |
| Last Inspection | 08/25/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NH00258 |
| Federal ID | NH00258 |
| More Info | State Dam Safety Program |