Tannery Pond Reservoir Report

Last Updated: December 16, 2025

Tannery Pond in Winchendon, Massachusetts, is a historic masonry dam completed in 1936 for hydroelectric purposes along the Millers River.


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Summary

With a dam height of 10 feet and a length of 248 feet, it has a storage capacity of 51 acre-feet and a maximum discharge rate of 3000 cubic feet per second. The spillway, controlled with a width of 144 feet, ensures safe water release during high flow events.

Managed by the Federal Energy Regulatory Commission, Tannery Pond has a low hazard potential and a very high risk assessment rating. Despite its age, the dam's condition assessment is not available, and it has not been inspected since August 2017. The emergency action plan was last revised in 2010, and there are no inundation maps or risk management measures in place.

As a significant piece of infrastructure in the region, Tannery Pond serves as a reminder of the intersection between water resources, climate considerations, and the need for proactive risk management to ensure its continued safety and functionality for both energy production and water management in the area.

Year Completed

1936

Dam Length

248

Dam Height

10

River Or Stream

Millers River

Primary Dam Type

Masonry

Surface Area

9

Drainage Area

54

Nid Storage

51

Outlet Gates

Slide (sluice gate) - 1

Hazard Potential

Low

Nid Height

10
       
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.