Tannery Pond Dam Reservoir Report

Last Updated: December 19, 2025

Tannery Pond Dam, located in Wilmot, New Hampshire, is a historic Earth dam completed in 1850 with a primary purpose of recreation.


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Summary

It stands at 12 feet high and spans 160 feet in length, holding a maximum storage capacity of 96 acre-feet. The dam is situated on Cassey Brook and is regulated by the NHDES Dam Bureau, with state permitting, inspection, and enforcement in place to ensure its safety and compliance.

Despite its low hazard potential and satisfactory condition assessment as of October 2016, Tannery Pond Dam poses a moderate risk (rating of 3) according to the data provided. With a drainage area of 14.85 square miles and a maximum discharge of 1100 cubic feet per second, the dam's spillway type is uncontrolled. While no Emergency Action Plan (EAP) or inundation maps are noted, regular inspections every six years help to monitor the dam's integrity and safety measures, with the risk management measures currently unspecified.

Enthusiasts of water resources and climate may find Tannery Pond Dam a fascinating subject for study, given its historical significance, recreational purpose, and regulatory oversight. Its location in the Merrimack County of New Hampshire, along with its moderate risk assessment and management considerations, offer a compelling case for further exploration and monitoring in the realm of dam safety and environmental impact.

Year Completed

1850

Dam Length

160

Dam Height

12

River Or Stream

CASSEY BROOK

Primary Dam Type

Earth

Surface Area

16

Drainage Area

14.85

Nid Storage

96

Hazard Potential

Low

Foundations

Unlisted/Unknown

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.