Plow Shop Pond Dam Reservoir Report

Last Updated: December 17, 2025

Plow Shop Pond Dam in Ayer, Massachusetts, is a privately owned earth dam constructed in 1856 for recreational purposes.


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Summary

The dam, standing at a height of 7 feet with a hydraulic height of 5.7 feet, impounds Nonacoicus Brook to create a reservoir with a storage capacity of 270 acre-feet. With a surface area of 28.4 acres and a drainage area of 15.8 square miles, the dam serves as a popular spot for outdoor activities and wildlife habitat in Middlesex County.

Despite its historical significance, Plow Shop Pond Dam is classified as having a low hazard potential due to poor condition assessment. The dam's spillway is uncontrolled, and it lacks outlet gates for controlled water release. With a risk assessment rating of moderate, there is a need for improved risk management measures to ensure the safety and integrity of the structure. The Department of Conservation and Recreation oversees the state regulation, inspection, and enforcement of the dam, highlighting the importance of ongoing maintenance and monitoring to mitigate potential risks and protect the surrounding community and environment.

Year Completed

1856

Dam Length

170

Dam Height

7

River Or Stream

NONACOICUS BROOK

Primary Dam Type

Earth

Surface Area

28.4

Hydraulic Height

5.7

Drainage Area

15.8

Nid Storage

270

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

7
       
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.
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Area Campgrounds