Big Brook Bog Dam Reservoir Report

Last Updated: December 12, 2025

Big Brook Bog Dam in Pittsburg, New Hampshire, is a state-regulated earth dam completed in 1946 for recreational purposes along Big Brook.


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Summary

With a dam height of 10.75 feet and a storage capacity of 250 acre-feet, this dam serves as a vital resource for the community. The dam has a spillway width of 21 feet and a significant hazard potential, but is currently in fair condition as of the last assessment in 2016.

Managed by the NHDES Dam Bureau, Big Brook Bog Dam provides a surface area of 36 acres and has a drainage area of 2.5 square miles. The dam has a maximum discharge capacity of 991 cubic feet per second and a normal storage capacity of 107 acre-feet. Despite its moderate risk rating, the dam has undergone regular inspections with the last one conducted in September 2020, ensuring the safety and integrity of this essential water resource in Coos County.

With its scenic location and importance for recreational activities, Big Brook Bog Dam is a key feature of the landscape in New Hampshire. While it faces potential risks, the dam's maintained condition and oversight by the state regulatory agency demonstrate a commitment to ensuring the safety and functionality of this essential water structure for the surrounding community and visitors alike.

Year Completed

1946

Dam Length

370

Dam Height

10.75

River Or Stream

BIG BROOK

Primary Dam Type

Earth

Surface Area

36

Drainage Area

2.5

Nid Storage

250

Hazard Potential

Significant

Foundations

Unlisted/Unknown

Nid Height

11
       
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.