Neponset River Dam - Lower Mills Reservoir Report
Last Updated: December 19, 2025
The Neponset River Dam at Lower Mills in Milton, Massachusetts, is a state-regulated structure designed for flood risk reduction along the Neponset River.
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Summary
This concrete dam, with a height of 15 feet and hydraulic height of 9.5 feet, serves to control the flow of the river and manage its drainage area of 109 square miles. Despite its significant hazard potential and poor condition assessment, the dam is inspected regularly by the Department of Conservation and Recreation to ensure its structural integrity and functionality.
With a storage capacity of 250 acre-feet, the Neponset River Dam plays a critical role in flood control for the surrounding area. Its primary purpose is flood risk reduction, and it is equipped with uncontrolled spillways to manage excess water flow during periods of heavy rainfall. The dam's location at Lower Mills on the Neponset River makes it an essential piece of infrastructure for protecting nearby communities from potential flooding events. While the dam's risk assessment is moderate, ongoing risk management measures are in place to mitigate any potential threats posed by its condition.
As a key component of the state's flood risk reduction strategy, the Neponset River Dam at Lower Mills is a vital structure for protecting the safety and well-being of residents in the Suffolk County area of Massachusetts. Despite its significant hazard potential and poor condition assessment, the dam continues to be inspected and regulated by the Department of Conservation and Recreation to ensure its continued effectiveness in managing the flow of the Neponset River. With its storage capacity, spillway design, and location along the river, the dam serves as a critical piece of infrastructure for maintaining the safety and security of the surrounding communities.
Dam Length |
140 |
Dam Height |
15 |
River Or Stream |
NEPONSET RIVER |
Primary Dam Type |
Concrete |
Surface Area |
64 |
Hydraulic Height |
9.5 |
Drainage Area |
109 |
Nid Storage |
250 |
Hazard Potential |
Significant |
Foundations |
Unlisted/Unknown |
Nid Height |
15 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Dam Data Reference
Condition Assessment
SatisfactoryNo existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.
Hazard Potential Classification
HighDams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.
Area Campgrounds
| Location | Reservations | Toilets |
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YMCA Camp
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Spang Camp Site
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Ponkapoag Camp of Appalachian Mountain Club
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Missionary Point
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Camp Christina Entrance
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Neponset River Dam - Lower Mills
Town Street 128, Braintree