Rosemary Lake Dam Reservoir Report

Last Updated: December 20, 2025

Rosemary Lake Dam, located in Needham, Massachusetts, serves as a critical water supply structure in the region.


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Summary

Completed in 1830, this earth dam stands at a height of 12 feet with a hydraulic height of 8 feet and a length of 440 feet. Managed by the Department of Conservation and Recreation, the dam has a storage capacity of 108 acre-feet and a surface area of 12.8 acres, providing essential water resources for the surrounding community.

With a high hazard potential, Rosemary Lake Dam has been assessed as satisfactory in condition, with the last inspection conducted in November 2017. Despite its age, the dam continues to meet regulatory standards and is regularly inspected by state authorities. The dam's spillway type is uncontrolled, highlighting the need for vigilant monitoring and maintenance to ensure the safety and stability of the structure.

While the risk assessment for Rosemary Lake Dam is moderate, there is a need for ongoing risk management measures to mitigate potential hazards. As a vital component of the local water supply infrastructure, the dam plays a crucial role in meeting the water needs of the community. With its historical significance and functional importance, Rosemary Lake Dam stands as a testament to the enduring legacy of water resource management in the region.

Year Completed

1830

Dam Length

440

Dam Height

12

River Or Stream

ROSEMARY BROOK

Primary Dam Type

Earth

Surface Area

12.8

Hydraulic Height

8

Drainage Area

1.1

Nid Storage

108

Hazard Potential

High

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.