Grist Mill Dam Reservoir Report

Last Updated: December 16, 2025

The Grist Mill Dam in Hopkinton, Massachusetts, is a gravity dam on Cold Spring Brook completed in 1900 for recreational purposes.


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Summary

It stands at a height of 10 feet with a hydraulic height of 8 feet, providing a storage capacity of 81.9 acre-feet. The dam is state-regulated by the Department of Conservation and Recreation, with regular inspections ensuring its fair condition and low hazard potential.

Situated in Middlesex County, the Grist Mill Dam is a vital part of the local landscape, offering a serene surface area of 11.1 acres for water enthusiasts to enjoy. Despite its age, the dam continues to serve its primary purpose of recreation, attracting visitors from near and far to appreciate its historical significance and natural beauty. With a moderate risk assessment rating, the dam is closely monitored to ensure the safety of both the structure and the surrounding environment.

Managed by the local government, the Grist Mill Dam remains a beloved landmark in the area, embodying a harmonious blend of history, engineering, and natural resource management. As climate change increasingly impacts water resources, the importance of maintaining and protecting such structures becomes even more crucial. From its construction in the early 20th century to its continued operation today, the Grist Mill Dam stands as a testament to the enduring relationship between humans and water, highlighting the need for sustainable practices to preserve our precious aquatic ecosystems.

Year Completed

1900

Dam Length

7

Dam Height

10

River Or Stream

COLD SPRING BROOK

Primary Dam Type

Gravity

Surface Area

11.1

Hydraulic Height

8

Drainage Area

4.2

Nid Storage

81.9

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

10
       
Seasonal Comparison

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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.