Millhurst Lake Dam Reservoir Report

Last Updated: December 8, 2025

Millhurst Lake Dam, located in Jamesburg, Monmouth County, New Jersey, is a local government-owned structure designed for recreational purposes.


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Summary

Built in 1915, this earth dam spans 270 feet in length and stands at a height of 23.4 feet, impounding the waters of Manalapan Brook to create Millhurst Lake with a storage capacity of 843 acre-feet. The dam's primary purpose is to provide recreational opportunities for the community, offering a surface area of 25 acres for various water-based activities.

Managed by the New Jersey Department of Environmental Protection, Millhurst Lake Dam is regulated, permitted, inspected, and enforced by state authorities to ensure its safety and compliance with standards. The dam's last inspection in June 2021 deemed its condition satisfactory, with a high hazard potential due to its location and storage capacity. While an Emergency Action Plan has not been prepared, the dam meets guidelines for risk assessment and management, although specific measures are not detailed in the available data. With its rich history and crucial role in providing recreational opportunities in the region, Millhurst Lake Dam serves as a reminder of the importance of water resource management and climate resilience in maintaining safe and enjoyable environments for communities to thrive.

Year Completed

1915

Dam Length

270

Dam Height

23.4

River Or Stream

Manalapan Brook

Primary Dam Type

Earth

Surface Area

25

Drainage Area

6.9

Nid Storage

843

Hazard Potential

High

Nid Height

23
       
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.