Green Mountain Lake Dam Reservoir Report

Last Updated: December 5, 2025

Green Mountain Lake Dam in Pawling, New York, is a significant masonry dam located on the Swamp River.


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Summary

Owned by the local government and regulated by the NYS DEC, this dam's primary purpose is recreation, providing a surface area of 32 acres and a storage capacity of 204 acre-feet. The dam stands at a height of 17 feet and stretches 110 feet in length, with an uncontrolled spillway width of 18 feet.

With a hazard potential rated as significant and a moderate risk assessment, Green Mountain Lake Dam is subject to regular inspections every four years, with the last assessment conducted in June 2017. Despite its condition being marked as "Not Rated," emergency action plans have been prepared, last revised in December 2020. The dam poses a moderate risk (level 3) and is not under the jurisdiction of the US Army Corps of Engineers.

Water resource and climate enthusiasts will find Green Mountain Lake Dam a captivating structure due to its recreational purpose, location on the Swamp River, and the measures in place to manage potential risks and emergencies. The dam's characteristics, including its masonry construction, storage capacity, and hazard potential, make it an intriguing site for those interested in water infrastructure and environmental management in the Dutchess County area of New York.

Dam Length

110

Dam Height

17

River Or Stream

SWAMP RIVER

Primary Dam Type

Masonry

Surface Area

32

Drainage Area

1.06

Nid Storage

204

Hazard Potential

Significant

Nid Height

17
       
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.