Neponset River Dam - Lower Mills
Neponset River Dam - Lower Mills is a concrete dam located in Suffolk County, Massachusetts. It carries a Significant hazard potential classification and has a poor condition assessment.
About Neponset River Dam - Lower Mills
The primary purpose of Neponset River Dam - Lower Mills 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 Ma Department Of Conservation & Recreation (state). It impounds the Neponset River near Milton.
The dam stands 15 feet tall and stretches 115 feet across, creates a reservoir covering 64 acres, has a maximum storage capacity of 250 acre-feet, and collects water from a drainage area of 109 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 poor, meaning the dam has recognized safety deficiencies that require remediation to address risks. An emergency action plan is in place for this dam. The most recent inspection on record was 03/18/2021.
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Location
| State | Massachusetts |
| County | Suffolk |
| Nearest City | Milton |
| River/Stream | Neponset River |
| Coordinates | 42.27074, -71.06881 |
Physical Characteristics
| Dam Type | Concrete |
| NID Height | 15 ft |
| Dam Length | 115 ft |
Storage & Hydraulics
| NID Storage | 250 acre-ft |
| Max Storage | 250 acre-ft |
| Normal Storage | 220 acre-ft |
| Surface Area | 64 acres |
| Drainage Area | 109 sq mi |
| Max Discharge | 5,300 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | MA Department of Conservation & Recreation |
| Owner Type | State |
| Hazard Classification | Significant |
| Condition Assessment | Poor |
| Last Inspection | 03/18/2021 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | MA01093 |
| Federal ID | MA01093 |
| More Info | State Dam Safety Program |