Mill River Dam is a concrete dam located in Hampshire County, Massachusetts, built in 1939. It carries a Significant hazard potential classification and has a satisfactory condition assessment.
Dam profile
NID height · 40 ft40 ft tall and 450 ft long, taller than 86% of U.S. dams with a recorded height. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic concrete gravity section and the water level is illustrative.
About Mill River Dam
The primary purpose of Mill River 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 City of Northampton (local government). It impounds the Mill River Diversion near Northampton.
The dam stands 40 feet tall and stretches 450 feet across, creates a reservoir covering 12 acres, has a maximum storage capacity of 165 acre-feet, and collects water from a drainage area of 54 square miles. Completed in 1939, 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 07/28/2020.
At 40 feet, this dam is taller than 86% of dams nationwide.
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Location
| State | Massachusetts |
| County | Hampshire |
| Nearest City | Northampton |
| River/Stream | Mill River Diversion |
| Coordinates | 42.30638, -72.64639 |
Physical Characteristics
| Dam Type | Concrete |
| NID Height | 40 ft |
| Dam Length | 450 ft |
| Year Completed | 1939 (87 years old) |
Storage & Hydraulics
| NID Storage | 165 acre-ft |
| Max Storage | 165 acre-ft |
| Normal Storage | 26 acre-ft |
| Surface Area | 12 acres |
| Drainage Area | 54 sq mi |
| Max Discharge | 30,000 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | City of Northampton |
| Owner Type | Local Government |
| Hazard Classification | Significant |
| Condition Assessment | Satisfactory |
| Last Inspection | 07/28/2020 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | MA01010 |
| Federal ID | MA01010 |
| More Info | State Dam Safety Program |