Blackwells Mills Dam is an earth dam located in Somerset County, New Jersey. It carries a Significant hazard potential classification and has a satisfactory condition assessment.
Dam profile
NID height · 20 ft20 ft tall and 500 ft long. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic embankment section and the water level is illustrative.
About Blackwells Mills Dam
The primary purpose of Blackwells Mills Dam is flood risk reduction. The dam is designed to control downstream flooding by temporarily storing excess water during storms and releasing it at a controlled rate. The dam is owned by Township of Hillsborough (local government). It impounds the Millstone River.
The dam stands 20 feet tall and stretches 500 feet across, creates a reservoir covering 1 acres, has a storage capacity of 10 acre-feet, and collects water from a drainage area of 0 square miles.
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 11/03/2023.
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Location
| State | New Jersey |
| County | Somerset |
| River/Stream | Millstone River |
| Coordinates | 40.47745, -74.59196 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 20 ft |
| Dam Height | 20 ft |
| Dam Length | 500 ft |
Storage & Hydraulics
| NID Storage | 10 acre-ft |
| Normal Storage | 10 acre-ft |
| Surface Area | 1 acres |
| Drainage Area | 0 sq mi |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | Township of Hillsborough |
| Owner Type | Local Government |
| Hazard Classification | Significant |
| Condition Assessment | Satisfactory |
| Last Inspection | 11/03/2023 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NJ00923 |
| Federal ID | NJ00923 |
| More Info | State Dam Safety Program |