Green Swamp #1 Dam Reservoir Report

Last Updated: December 6, 2025

Green Swamp #1 Dam, located in Bloomingdale Borough, Passaic, New Jersey, is a state-owned earth dam with a primary purpose of water supply.


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Summary

Completed in 1926, this dam stands at a height of 29 feet and spans a length of 640 feet, creating a reservoir with a normal storage capacity of 41,700 acre-feet and a surface area of 2,400 acres. It is regulated, permitted, inspected, and enforced by the New Jersey Department of Environmental Protection, ensuring its safe operation and maintenance.

The dam, situated on Post Brook, falls under the jurisdiction of the Philadelphia District of the US Army Corps of Engineers. Its hazard potential is classified as high, yet its condition assessment as of October 2021 was deemed satisfactory. With a biennial inspection frequency, the dam has a comprehensive Emergency Action Plan in place, last updated in February 2022. While there are no associated spillways or locks, Green Swamp #1 Dam remains a crucial infrastructure for water resource management in the region, highlighting the importance of ongoing monitoring and risk management measures.

Representing a vital component of New Jersey's water supply infrastructure, Green Swamp #1 Dam plays a key role in flood control and water storage for the surrounding area. As part of Congressional District 11, it is supported by Representative Mikie Sherrill and serves as a critical asset for ensuring water security and environmental protection. With its historical significance and ongoing regulatory oversight, the dam exemplifies the intersection of engineering, policy, and climate resilience in safeguarding water resources for future generations.

Year Completed

1926

Dam Length

640

Dam Height

29

River Or Stream

Post Brook

Primary Dam Type

Earth

Surface Area

2400

Drainage Area

94.4

Nid Storage

41700

Hazard Potential

High

Nid Height

29
       
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.