Apthorp
Apthorp is a concrete dam located in Grafton County, New Hampshire, built in 1936. It carries a Significant hazard potential classification and has a satisfactory condition assessment.
About Apthorp
The primary purpose of Apthorp 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 White Mountain Hydroelectric Corporation (private). It impounds the Ammonoosuc River near Littleton.
The dam stands 24 feet tall and stretches 235 feet across, creates a reservoir covering 20 acres, has a maximum storage capacity of 210 acre-feet, and collects water from a drainage area of 205 square miles. Completed in 1936, the structure is well-established, with more than 75 years of service.
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 satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 08/17/2022.
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Location
| State | New Hampshire |
| County | Grafton |
| Nearest City | Littleton |
| River/Stream | Ammonoosuc River |
| Coordinates | 44.30620, -71.74540 |
Physical Characteristics
| Dam Type | Concrete |
| NID Height | 24 ft |
| Dam Height | 24 ft |
| Dam Length | 235 ft |
| Year Completed | 1936 (90 years old) |
Storage & Hydraulics
| NID Storage | 210 acre-ft |
| Max Storage | 210 acre-ft |
| Normal Storage | 210 acre-ft |
| Surface Area | 20 acres |
| Drainage Area | 205 sq mi |
| Max Discharge | 14,800 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner | White Mountain Hydroelectric Corporation |
| Owner Type | Private |
| Hazard Classification | Significant |
| Condition Assessment | Satisfactory |
| Last Inspection | 08/17/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NH00611 |
| Federal ID | NH00611 |
| More Info | State Dam Safety Program |