Lower Twin Lakes Dam Reservoir Report

Last Updated: December 6, 2025

Lower Twin Lakes Dam, located in Wayne, New Jersey, is a privately owned earth dam that was completed in 1927.


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Summary

The dam stands at a height of 10 feet and spans 210 feet in length, creating a reservoir with a storage capacity of 128 acre-feet. The primary purpose of the dam is for recreation, providing a serene and picturesque setting for water enthusiasts to enjoy activities such as fishing, boating, and picnicking.

Managed by the New Jersey Department of Environmental Protection, Lower Twin Lakes Dam is subject to state regulation, permitting, inspection, and enforcement to ensure its safety and integrity. The dam's condition assessment in August 2021 deemed it satisfactory, although it carries a significant hazard potential. Despite this, the dam has not undergone any major modifications in recent years, and its emergency action plan was last revised in 2013.

Situated along the Post Brook river in Passaic County, Lower Twin Lakes Dam serves as a vital water resource for the surrounding area, with a drainage area of 8.8 square miles and a surface area of 40 acres. While the dam's risk assessment, inundation maps, and risk management measures remain unspecified, its role in providing recreational opportunities and water storage highlights its importance in the local ecosystem and community.

Year Completed

1927

Dam Length

210

Dam Height

10

River Or Stream

Post Brook

Primary Dam Type

Earth

Surface Area

40

Drainage Area

8.8

Nid Storage

128

Hazard Potential

Significant

Nid Height

10
       
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.