Quaddick Reservoir Dike Reservoir Report

Last Updated: December 5, 2025

The Quaddick Reservoir Dike, located in Windham, Connecticut, is a state-owned earth dam completed in 1900 primarily for recreational purposes.


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Summary

The dam, standing at a height of 18.5 feet and with a length of 420 feet, holds a maximum storage capacity of 5,100 acre-feet and covers a surface area of 467 acres. The reservoir, situated on the Fivemile River, serves as a popular spot for outdoor activities such as boating, fishing, and wildlife observation.

Despite its fair condition assessment and high hazard potential, the Quaddick Reservoir Dike is regulated, inspected, and permitted by the Connecticut Department of Energy and Environmental Protection (DEEP). With a drainage area of 24.2 square miles and a normal storage capacity of 4,280 acre-feet, the dam plays a crucial role in flood control and water resource management in the region. The structure is also associated with one other dam, CT00184, and undergoes inspections every two years to ensure its integrity and safety.

Owned and operated by the state, the Quaddick Reservoir Dike is a key component of Connecticut's water infrastructure. With its historical significance dating back over a century, the dam continues to provide vital recreational opportunities while simultaneously serving as a vital resource for climate enthusiasts and water resource management professionals alike. Its location in Thompson, along with its impressive storage capacity and role in flood control, highlights the importance of this earth dam in the region's overall water management system.

Year Completed

1900

Dam Length

420

Dam Height

18.5

River Or Stream

FIVEMILE RIVER

Primary Dam Type

Earth

Surface Area

467

Drainage Area

24.2

Nid Storage

5100

Hazard Potential

High

Foundations

Rock, Soil

Nid Height

19
       
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.