Lost Lake Dam Reservoir Report

Last Updated: December 17, 2025

Lost Lake Dam in Groton, Massachusetts, stands as a concrete gravity dam with a primary purpose of recreation.


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Summary

Completed in 1910, the dam has a height of 10 feet and a hydraulic height of 8 feet, providing a storage capacity of 1,960 acre-feet. The dam, located on Martin's Pond Brook, serves as a popular spot for outdoor enthusiasts seeking to enjoy the surrounding surface area of 300 acres for recreational activities.

Maintained by the Department of Conservation and Recreation, the dam is regulated by the state of Massachusetts, with inspections occurring every two years. Despite being categorized as having a high hazard potential, the dam's condition is currently assessed as satisfactory. In case of emergencies, the dam has an Emergency Action Plan in place, last revised in August 2016. With its controlled spillway and very high risk assessment rating, the Lost Lake Dam presents a crucial infrastructure for water resource management and climate resilience efforts in the region.

Lost Lake Dam not only serves as a recreational hub but also plays a key role in water storage and management in Middlesex County. With its historical significance dating back over a century, the dam continues to be a focal point for water resource and climate enthusiasts. As efforts to enhance risk management measures and emergency preparedness are ongoing, the Lost Lake Dam remains a vital asset for the community, highlighting the intersection of conservation, recreation, and infrastructure in the region.

Year Completed

1910

Dam Length

100

Dam Height

10

River Or Stream

MARTIN'S POND BROOK

Primary Dam Type

Concrete

Surface Area

300

Hydraulic Height

8

Drainage Area

5.2

Nid Storage

1960

Hazard Potential

High

Foundations

Unlisted/Unknown

Nid Height

10
       
Seasonal Comparison

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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.