Tillson Lake Dam Reservoir Report

Last Updated: December 6, 2025

Tillson Lake Dam, located in Rutsonville, New York, is a state-owned structure built in 1930 primarily for recreational purposes.


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Summary

With a height of 39 feet and a length of 308 feet, the dam impounds the Palmaghatt Kill stream, creating a surface area of 23 acres and a drainage area of 4.78 square miles. The dam has a maximum storage capacity of 394 acre-feet and a normal storage of 230 acre-feet, making it an important water resource for the surrounding area.

Despite its recreational significance, Tillson Lake Dam poses a high hazard potential with poor condition assessment, as reported in the last inspection conducted in April 2020. The dam's spillway type is uncontrolled with a width of 55 feet, and it has a maximum discharge capacity of 2690 cubic feet per second. With a risk assessment rating of moderate (3), there is a need for enhanced risk management measures to address potential safety concerns and ensure the structural integrity of the dam for both water resource conservation and climate resilience in the region.

As a key component of the water infrastructure in Ulster County, New York, Tillson Lake Dam serves as a vital resource for local residents and visitors alike. With ongoing state regulation, inspection, and enforcement by the New York State Department of Environmental Conservation, efforts are being made to mitigate risks associated with the dam and maintain its functionality for recreational and water management purposes. Continued monitoring and maintenance of Tillson Lake Dam are essential to safeguarding the surrounding community and preserving the dam's role in water resource management and climate adaptation efforts in the region.

Year Completed

1930

Dam Length

308

Dam Height

39

River Or Stream

PALMAGHATT KILL

Primary Dam Type

Earth

Surface Area

23

Drainage Area

4.78

Nid Storage

394

Hazard Potential

High

Nid Height

39
       
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.