Rainbow Lake Dam Reservoir Report

Last Updated: December 5, 2025

Rainbow Lake Dam, located in Pittsgrove Township, New Jersey, is a state-regulated structure on Troy Brook with a primary purpose of recreation.


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Summary

Built in 1774, this earth dam stands at a height of 20 feet and spans 900 feet in length, providing a storage capacity of 240 acre-feet. The dam covers a surface area of 80 acres and serves a drainage area of 53.1 square miles.

Despite its age, Rainbow Lake Dam is assessed to be in fair condition with a significant hazard potential. The last inspection in April 2021 indicated a need for regular monitoring and maintenance, with an inspection frequency set at every two years. Its emergency action plan was last revised in April 2020, emphasizing the importance of preparedness and response measures in the event of a dam failure. With a noteworthy risk profile, Rainbow Lake Dam remains a critical structure requiring ongoing attention and management to ensure public safety and environmental protection in Salem County, New Jersey.

As a key feature in the recreation landscape of the area, Rainbow Lake Dam plays a vital role in water resource management and climate resilience. Its historical significance as one of the early dams in the region adds to its cultural and environmental value, making it a focal point for enthusiasts interested in the intersection of water infrastructure, climate adaptation, and sustainable development in New Jersey.

Year Completed

1774

Dam Length

900

Dam Height

20

River Or Stream

Troy Brook

Primary Dam Type

Earth

Surface Area

80

Drainage Area

53.1

Nid Storage

240

Hazard Potential

Significant

Nid Height

20
       
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.