Lower Lake Dam Reservoir Report

Last Updated: January 2, 2026

Lower Lake Dam, located in Shirley, New York, is a vital structure for recreation purposes, serving as a popular spot for water enthusiasts.


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Summary

Built in 1940, this earth dam stands at a height of 12 feet and stretches over 600 feet in length, creating a surface area of 26 acres and providing a maximum storage capacity of 156 acre-feet. The dam is situated on the Carman River and is regulated by the NYS DEC, with state inspection, permitting, and enforcement in place to ensure its safety and functionality.

Despite its low hazard potential, Lower Lake Dam is considered to have a very high risk factor, marked as a risk level 1 structure. While the dam's condition assessment is not rated, regular inspections are conducted to monitor its integrity. Emergency action plans and risk management measures are crucial for the dam's operation, although specific details on these aspects are currently not available. Overall, Lower Lake Dam serves as both a recreational asset and a critical infrastructure piece in the water resource management of Suffolk County, New York.

Year Completed

1940

Dam Length

600

Dam Height

12

River Or Stream

CARMANS RIVER

Primary Dam Type

Earth

Surface Area

26

Drainage Area

71

Nid Storage

156

Hazard Potential

Low

Nid Height

12
       
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.