Hidden Valley Lake Dam Reservoir Report

Last Updated: December 10, 2025

Hidden Valley Lake Dam, located in Andover, New Jersey, stands as a private-owned structure on the Pequest River-TR.


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Summary

Built in 1967 primarily for recreational purposes, this earth and gravity dam spans 350 feet in length and reaches a height of 25 feet, providing a storage capacity of 645 acre-feet. Despite its significant hazard potential, the dam is currently assessed to be in poor condition, prompting regular inspections every two years to ensure public safety.

Managed by the New Jersey Department of Environmental Protection, Hidden Valley Lake Dam is a vital component of the local water resource infrastructure, offering a surface area of 44 acres within its reservoir and serving a drainage area of 1.8 square miles. With a maximum discharge capacity of 913 cubic feet per second, the dam plays a crucial role in flood control and water management in Sussex County. However, ongoing maintenance and improvement efforts are necessary to address the dam's current condition and potential risks.

As climate change continues to impact water resources across the region, the maintenance and operation of Hidden Valley Lake Dam will be essential in ensuring the safety and sustainability of the surrounding communities. With its historical significance and recreational value, this dam serves as a reminder of the delicate balance between human development and environmental stewardship in the face of evolving climate challenges.

Year Completed

1967

Dam Length

350

Dam Height

25

River Or Stream

Pequest River-TR

Primary Dam Type

Earth

Surface Area

44

Drainage Area

1.8

Nid Storage

645

Hazard Potential

Significant

Nid Height

25
       
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.