Brooklyn
Brooklyn is a dam located in Coos County, New Hampshire, built in 1919. It carries a Significant hazard potential classification and has a unsatisfactory condition assessment.
About Brooklyn
The primary purpose of Brooklyn 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 5440 Hydro Inc. (private). It impounds the Upper Ammonoosuc River near Groveton.
The dam stands 19 feet tall and stretches 275 feet across, creates a reservoir covering 26 acres, has a maximum storage capacity of 240 acre-feet, and collects water from a drainage area of 254 square miles. Completed in 1919, 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 unsatisfactory, indicating serious safety deficiencies exist that require immediate attention or remedial action. An emergency action plan is in place for this dam. The most recent inspection on record was 07/14/2025.
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Location
| State | New Hampshire |
| County | Coos |
| Nearest City | Groveton |
| River/Stream | Upper Ammonoosuc River |
| Coordinates | 44.60008, -71.50526 |
Physical Characteristics
| NID Height | 19 ft |
| Dam Height | 19 ft |
| Dam Length | 275 ft |
| Year Completed | 1919 (107 years old) |
Storage & Hydraulics
| NID Storage | 240 acre-ft |
| Max Storage | 240 acre-ft |
| Normal Storage | 50 acre-ft |
| Surface Area | 26 acres |
| Drainage Area | 254 sq mi |
| Max Discharge | 12,500 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner | 5440 Hydro Inc. |
| Owner Type | Private |
| Hazard Classification | Significant |
| Condition Assessment | Unsatisfactory |
| Last Inspection | 07/14/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NH00148 |
| Federal ID | NH00148 |
| More Info | State Dam Safety Program |