Keswick Grove Lower Dam Reservoir Report

Last Updated: December 8, 2025

Keswick Grove Lower Dam, located in Keswick Grove, New Jersey, is a privately owned earth dam built in 1898 primarily for recreational purposes.


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Summary

The dam, standing at a height of 7.8 feet and with a length of 200 feet, impounds Wrangel Brook, creating a reservoir with a storage capacity of 106 acre-feet. Despite its age, the dam is in satisfactory condition, with a low hazard potential, as assessed during the last inspection in August 2020.

The dam falls under the regulatory jurisdiction of the New Jersey Department of Environmental Protection (NJDEP), with state permitting, inspection, and enforcement measures in place to ensure its safety and compliance with regulations. In the event of an emergency, the dam is equipped with emergency action plans, although specific details on their preparation and guidelines adherence are not provided in the data. With its serene location and recreational purpose, Keswick Grove Lower Dam serves as a tranquil spot for water resource and climate enthusiasts to appreciate the intersection of human engineering with the natural environment in Ocean County, New Jersey.

Year Completed

1898

Dam Length

200

Dam Height

7.8

River Or Stream

Wrangel Brook

Primary Dam Type

Earth

Surface Area

9

Drainage Area

1

Nid Storage

106

Hazard Potential

Low

Nid Height

8
       
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.