Grover's Mill Dam Reservoir Report

Last Updated: December 7, 2025

Grover's Mill Dam, located in West Windsor, New Jersey, is a local government-owned structure that serves primarily for recreation purposes.


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Summary

Built in 1931, this earth dam stands at a height of 14.5 feet and has a length of 430 feet, creating a storage capacity of 150 acre-feet along Big Bear Brook. The dam is regulated by the New Jersey Department of Environmental Protection and undergoes regular inspections to ensure its safety and compliance with state regulations.

Despite being classified as having a significant hazard potential, Grover's Mill Dam is currently assessed as being in fair condition as of the last inspection in June 2021. The dam has a drainage area of 12.3 square miles and a maximum discharge capacity of 480 cubic feet per second. It is situated in a picturesque setting with a surface area of 45 acres, offering recreational opportunities for visitors. With its historical significance and contribution to the local landscape, Grover's Mill Dam stands as a notable water resource structure in Mercer County, New Jersey.

Year Completed

1931

Dam Length

430

Dam Height

14.5

River Or Stream

Big Bear Brook

Primary Dam Type

Earth

Surface Area

45

Drainage Area

12.3

Nid Storage

150

Hazard Potential

Significant

Nid Height

15
       
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.