Quillinan Reservoir Dam Reservoir Report

Last Updated: December 5, 2025

Quillinan Reservoir Dam, located in Ansonia, Connecticut, is a concrete structure completed in 1880 with a primary purpose of recreation.


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Summary

The dam stands at a height of 19 feet and stretches 575 feet in length, creating a surface area of 12 acres and serving a drainage area of 2.67 square miles. Despite its historical significance, the dam poses a high hazard potential and has been assessed to be in fair condition as of October 2020.

Managed by the State of Connecticut Department of Energy and Environmental Protection (DEEP), the Quillinan Reservoir Dam is regulated, permitted, inspected, and enforced by state authorities. The dam features an uncontrolled spillway with a width of 34 feet, posing moderate risks that are closely monitored with a regular inspection frequency of every two years. Although the dam does not have associated locks or outlet gates, its emergency action plan (EAP) was last revised in May 2016, ensuring preparedness for potential hazards.

For water resource and climate enthusiasts, the Quillinan Reservoir Dam represents a historical landmark in Connecticut's water management infrastructure, offering recreational opportunities while facing operational challenges due to its high hazard potential. As efforts continue to monitor and manage the dam's risks, ongoing inspections and risk assessments play a crucial role in maintaining the safety and integrity of this significant structure in the Beaver Brook watershed.

Year Completed

1880

Dam Length

575

Dam Height

19

River Or Stream

BEAVER BROOK

Primary Dam Type

Concrete

Surface Area

12

Drainage Area

2.67

Hazard Potential

High

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.