First Connecticut Lake Dam Reservoir Report

Last Updated: December 11, 2025

First Connecticut Lake Dam, located in Pittsburg, New Hampshire, stands as a vital structure along the Connecticut River, serving a primary purpose of hydroelectric power generation.


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Summary

Completed in 1930, this earth dam boasts a height of 56 feet and a length of 1117 feet, providing a storage capacity of 114,000 acre-feet and a surface area of 2800 acres. With a maximum discharge capacity of 20,600 cubic feet per second and a spillway width of 338 feet, the dam plays a crucial role in managing water resources in the region.

Despite its age, the dam is regulated, inspected, and enforced by the New Hampshire Department of Environmental Services Dam Bureau, ensuring its structural integrity and operational safety. The dam has a fair condition assessment as of June 2015, with a high hazard potential and moderate risk assessment rating. While the dam meets guidelines for emergency action plans, there is room for improvement in terms of risk management measures and inundation mapping. Enthusiasts of water resources and climate will find First Connecticut Lake Dam to be a fascinating example of infrastructure that combines historical significance with environmental stewardship and hydroelectric innovation.

Year Completed

1930

Dam Length

1117

Dam Height

56

River Or Stream

CONNECTICUT RIVER

Primary Dam Type

Earth

Surface Area

2800

Drainage Area

82

Nid Storage

114000

Hazard Potential

High

Foundations

Unlisted/Unknown

Nid Height

56
       
Seasonal Comparison

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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.