First Conn Lake South Bay Dike Reservoir Report

Last Updated: December 11, 2025

First Conn Lake South Bay Dike in Pittsburg, New Hampshire, is a private earth dam on the Connecticut River primarily used for recreation.


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Summary

Standing at a height of 14 feet and spanning 390 feet in length, this structure has a normal storage capacity of 15,950 acre-feet and a maximum storage of 38,950 acre-feet. With a surface area of 2,800 acres and a drainage area of 82 square miles, this dam plays a crucial role in managing water resources in the region.

Maintained and regulated by the NHDES Dam Bureau, First Conn Lake South Bay Dike has a low hazard potential and is currently assessed to be in fair condition as of June 2015. Despite its moderate risk level, the dam has not undergone any recent modifications and has an inspection frequency of 6 years. While the dam does not have a designated Emergency Action Plan (EAP) or inundation maps prepared, its risk management measures and overall safety protocols are continuously monitored to ensure public safety and environmental protection in the event of an emergency.

Overall, First Conn Lake South Bay Dike serves as a vital recreational structure on the Connecticut River, showcasing the importance of proper dam management and maintenance to safeguard water resources and mitigate potential risks associated with dam failure. As climate change continues to impact water availability and extreme weather events, the resilience and sustainability of such structures are paramount in ensuring the safety and well-being of local communities and ecosystems.

Dam Length

390

Dam Height

14

River Or Stream

CONNECTICUT RIVER

Primary Dam Type

Earth

Surface Area

2800

Drainage Area

82

Nid Storage

38950

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

14
       
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.