Upper Pond Dam (Aka Holbrook ) Reservoir Report

Last Updated: December 5, 2025

Upper Pond Dam, also known as Holbrook Dam, is a privately owned structure located in Lyme, Connecticut.


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Summary

Built in 1860, this masonry dam serves primarily for recreational purposes, providing a surface area of 13 acres and a storage capacity of 54 acre-feet. The dam stands at a height of 12 feet and stretches 90 feet in length, controlling the flow of water from Joshua Creek.

Managed by the Connecticut Department of Energy and Environmental Protection (DEEP), Upper Pond Dam is regulated, inspected, and enforced by state authorities to ensure its safety and compliance with regulations. Despite being rated as having a significant hazard potential, the dam's condition is deemed satisfactory as of the last inspection in August 2018. The dam has a spillway width of 31 feet and a maximum discharge capacity of 145 cubic feet per second.

With its historical significance dating back over a century, Upper Pond Dam stands as a testament to both the engineering marvels of the past and the ongoing efforts to maintain and safeguard water resources in the face of changing climate conditions. As enthusiasts of water resources and climate issues, the preservation and responsible management of structures like Upper Pond Dam serve as important examples of the intersection between human development and environmental stewardship in the modern era.

Year Completed

1860

Dam Length

90

Dam Height

12

River Or Stream

JOSHUA CREEK

Primary Dam Type

Masonry

Surface Area

13

Drainage Area

2.09

Nid Storage

54

Hazard Potential

Significant

Nid Height

12
       
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.