Neponset River Dam Reservoir Report

Last Updated: December 19, 2025

The Neponset River Dam, located in Walpole, Massachusetts, is a masonry dam with a primary purpose of "Other." Completed in 1850, this historic structure stands 15 feet high and has a hydraulic height of 11 feet, with a storage capacity of 153 acre-feet.


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Summary

The dam regulates the flow of the Neponset River and is under the jurisdiction of the Department of Conservation and Recreation in Massachusetts.

Despite its low hazard potential, the Neponset River Dam is currently in poor condition and is rated as having a moderate risk level. The last inspection in 2009 revealed the need for improvements, yet the structure remains in operation. With a drainage area of 10.9 square miles, the dam plays a crucial role in managing water resources and protecting the surrounding community from potential flooding events.

As climate change continues to impact water resources and infrastructure, the Neponset River Dam serves as a reminder of the importance of maintaining and updating aging structures to ensure the safety and resilience of our water systems. With a risk management plan in place and regular inspections, efforts can be made to address the dam's poor condition and enhance its ability to withstand future challenges posed by a changing climate.

Year Completed

1850

Dam Length

150

Dam Height

15

River Or Stream

NEPONSET RIVER

Primary Dam Type

Masonry

Hydraulic Height

11

Drainage Area

10.9

Nid Storage

153

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

15
       
Seasonal Comparison

Weather Forecast

Dam Data Reference

Condition Assessment

Satisfactory
No 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

High
Dams 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.