Mountain Lake Dam Reservoir Report

Last Updated: December 6, 2025

Mountain Lake Dam, located in Lewbeach, New York, is a privately owned structure with a primary purpose of recreation.


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Summary

The earth-type dam, completed in 1930, stands at 15 feet high and spans a length of 500 feet, with a storage capacity of 118 acre-feet. Situated on the TR-BIG POND river or stream, the dam features a controlled spillway with a width of 20 feet and has a low hazard potential rating. Despite not being rated for condition assessment, the dam has undergone state regulation, permitting, inspection, and enforcement, ensuring its safety and compliance with standards.

The dam's risk assessment categorizes it as having a very high risk level, emphasizing the need for effective risk management measures. Although the last inspection dates back to 1996, the dam's emergency action plan status, inundation maps, and compliance with guidelines remain unclear. With a maximum discharge capacity of 240 cubic feet per second, the dam serves as a vital recreational resource in Delaware County, offering a surface area of 19 acres for various activities. Even though it is not federally owned or funded, the Mountain Lake Dam plays a crucial role in water resource management and climate preservation efforts in the region.

In the realm of water resource and climate conservation, Mountain Lake Dam's significance lies in its role as a recreational asset with controlled water management capabilities. As a privately owned structure regulated by the NYS DEC, the dam is vital for both local residents and visitors seeking outdoor activities. With its low hazard potential and a history dating back to the early 20th century, the dam stands as a testament to sustainable infrastructure development and the need for ongoing risk assessment and management practices in the face of evolving climate challenges.

Year Completed

1930

Dam Length

500

Dam Height

15

River Or Stream

TR-BIG POND

Primary Dam Type

Earth

Surface Area

19

Nid Storage

118

Hazard Potential

Low

Nid Height

15
       
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.