Thayer Pond Dam Reservoir Report

Last Updated: December 11, 2025

Thayer Pond Dam, located in Worcester County, Massachusetts, is a State-owned structure regulated by the Department of Conservation and Recreation.


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Summary

Built in 1930, this Earth-type dam stands at a height of 3.16 feet and serves multiple purposes, with a primary function classified as 'Other'. The dam impounds Mill Brook, creating a reservoir with a storage capacity of 108.8 acre-feet and a normal storage level of 77.55 acre-feet.

Despite being classified as having a low hazard potential, the condition assessment of Thayer Pond Dam in 2009 was deemed unsatisfactory. With an inspection frequency of 10 years, the dam is monitored for safety but lacks a current Emergency Action Plan (EAP) and updated inundation maps. The risk assessment for the dam is moderate, indicating a level 3 risk rating, highlighting the need for continued monitoring and potential risk management measures to ensure the safety of the surrounding area in case of a breach or emergency situation.

For water resource and climate enthusiasts, Thayer Pond Dam presents an intriguing case study of a historic dam with varying levels of risk and maintenance challenges. As a vital component of the local water infrastructure system, the dam's management and upkeep are crucial for both water supply and environmental protection. With its unique characteristics and regulatory oversight, Thayer Pond Dam serves as a focal point for discussions on dam safety, risk assessment, and emergency preparedness in the context of changing climate conditions.

Year Completed

1930

Dam Length

300

Dam Height

3.16

River Or Stream

MILL BROOK

Primary Dam Type

Earth

Surface Area

0.09

Hydraulic Height

6.13

Drainage Area

2.46

Nid Storage

108.8

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

6
       
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.