Grupes Reservoir Dam Reservoir Report

Last Updated: December 5, 2025

Grupes Reservoir Dam, located in Fairfield, Connecticut, is a pivotal structure managed by the local government for water supply purposes.


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Summary

Completed in 1871, this concrete dam stands at a height of 24 feet and has a length of 235 feet, providing a storage capacity of 311 acre-feet. The dam overlooks the scenic Silvermine River and serves as a vital resource for the surrounding community.

Despite its historical significance, Grupes Reservoir Dam faces challenges with a high hazard potential and poor condition assessment, highlighting the need for regular inspections and maintenance. The dam's spillway type is uncontrolled, with a spillway width of 49 feet, emphasizing the importance of effective risk management measures. With a moderate risk assessment rating of 3, efforts are underway to ensure the safety and functionality of this essential water infrastructure for the region.

As climate change impacts water resources, the resilience and sustainability of dams like Grupes Reservoir are crucial for mitigating risks and ensuring reliable water supply. The dam's location in New Canaan underscores its strategic importance in managing water resources and protecting against potential hazards. For water resource and climate enthusiasts, Grupes Reservoir Dam presents a compelling case study on the intersection of infrastructure, environmental stewardship, and community resilience in the face of evolving climate challenges.

Year Completed

1871

Dam Length

235

Dam Height

24

River Or Stream

SILVERMINE RIVER

Primary Dam Type

Concrete

Surface Area

23

Drainage Area

10.2

Nid Storage

311

Outlet Gates

Valve

Hazard Potential

High

Foundations

Rock

Nid Height

24
       
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.