Nassau Lake Dam Reservoir Report

Last Updated: December 19, 2025

Nassau Lake Dam, located in Nassau, New York, is a privately owned structure built in 1792 primarily for recreation purposes.


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Summary

With a height of 10 feet and a length of 200 feet, this earth dam holds a storage capacity of 550 acre-feet, with a normal storage level of 380 acre-feet. The dam, situated on Valatie Kill, has a surface area of 173 acres and serves as a significant hazard potential due to its uncontrolled spillway design and a maximum discharge capacity of 990 cubic feet per second.

Despite being a privately owned structure, Nassau Lake Dam is regulated, inspected, and enforced by the New York State Department of Environmental Conservation (NYS DEC), ensuring its compliance with safety standards. The dam has not been rated for its condition assessment, but a moderate risk level of 3 has been assigned to it. Emergency Action Plans have been prepared for the dam, although they may need updates to meet current guidelines. With its historical significance and recreational purpose, Nassau Lake Dam stands as a vital water resource in Rensselaer County, New York, for both residents and visitors to enjoy.

Year Completed

1792

Dam Length

200

Dam Height

10

River Or Stream

VALATIE KILL

Primary Dam Type

Earth

Surface Area

173

Drainage Area

16.5

Nid Storage

550

Hazard Potential

Significant

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.