Lower Long Pond Dam Reservoir Report

Last Updated: December 17, 2025

Lower Long Pond Dam, located in Ayer, Massachusetts, is a privately owned structure regulated by the Department of Conservation and Recreation.


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Summary

Built in 1961, this Earth dam stands at a height of 8 feet and has a hydraulic height of 1.5 feet. Its primary purpose is listed as "Other" and serves as a crucial component in managing the water resources of the tributary of Long Pond Brook.

The dam has a storage capacity of 103.1 acre-feet, with a normal storage level of 21.5 acre-feet. While its hazard potential is categorized as low, the condition assessment was rated as fair during the last inspection in 2009. The risk assessment for Lower Long Pond Dam indicates a moderate risk level, highlighting the importance of ongoing monitoring and maintenance to ensure its structural integrity and continued functionality for water resource management in the region.

Climate and water resource enthusiasts will find Lower Long Pond Dam an interesting case study in dam infrastructure, regulatory oversight, and risk management. With its historical significance dating back to the 1960s, this dam plays a vital role in controlling water flow and storage in the area. Ongoing inspections and maintenance efforts are essential to mitigate potential risks and ensure the safety and efficiency of this important water management structure.

Year Completed

1961

Dam Length

150

Dam Height

8

River Or Stream

TRIBUTARY OF LONG POND BROOK

Primary Dam Type

Earth

Hydraulic Height

1.5

Nid Storage

103.1

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

8
       
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.