Grenloch Lake Dam Reservoir Report

Last Updated: December 5, 2025

Located in Washington Township, New Jersey, Grenloch Lake Dam stands tall as a vital structure along the South Branch Timber Creek.


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Summary

Built in 1907, this earth dam serves multiple purposes, primarily catering to recreation and water supply needs. With a dam height of 21 feet and a length of 250 feet, it boasts a storage capacity of 272 acre-feet, providing essential water resources to the surrounding area.

Regulated by the New Jersey Department of Environmental Protection, Grenloch Lake Dam undergoes regular inspections to ensure its structural integrity and safety. Classified with a significant hazard potential and a fair condition assessment, the dam is equipped to handle emergencies effectively. Despite its age, the dam continues to serve the community reliably, with a surface area of 21 acres and a drainage area of 14.6 square miles, showcasing its importance in water management and recreational activities.

With its historical significance and impact on water resources, Grenloch Lake Dam stands as a testament to efficient dam engineering and management practices. As a focal point for water supply and recreation in Gloucester County, this earth dam plays a crucial role in maintaining the ecological balance and meeting the needs of the local community. Its strategic location and storage capacity make it a valuable asset in water resource management, reflecting the intersection of environmental stewardship and public utility in the region.

Year Completed

1907

Dam Length

250

Dam Height

21

River Or Stream

South Branch Timber Creek

Primary Dam Type

Earth

Surface Area

21

Drainage Area

14.6

Nid Storage

272

Hazard Potential

Significant

Nid Height

21
       
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.