Regional Detention Basin Dam E Reservoir Report

Last Updated: December 7, 2025

Regional Detention Basin Dam E, located in Hillsborough Township, Somerset County, New Jersey, is a crucial structure designed for flood risk reduction along the Royce Brook.


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Summary

Owned by the local government and regulated by the New Jersey Department of Environmental Protection, this earth-type dam stands at a height of 17.4 feet and has a storage capacity of 193 acre-feet. With a significant hazard potential, the dam has been assessed as satisfactory during its last inspection in November 2020.

Constructed with a length of 750 feet, the dam serves as a critical barrier to manage stormwater and prevent flooding in the surrounding area. Its primary purpose is flood risk reduction, with a normal storage capacity of 10 acre-feet and a maximum discharge rate of 5466 cubic feet per second. While the dam has not undergone any modifications since its completion, it is subject to regular inspections every two years to ensure its structural integrity and operational effectiveness.

Overall, Regional Detention Basin Dam E plays a vital role in safeguarding the community against potential flood events and managing water resources in the region. With its strategic location and design, this dam exemplifies the importance of proactive infrastructure development for climate resilience and disaster mitigation in the face of changing environmental conditions.

Dam Length

750

Dam Height

17.4

River Or Stream

Royce Brook

Primary Dam Type

Earth

Surface Area

1

Drainage Area

2.8

Nid Storage

193

Hazard Potential

Significant

Nid Height

17
       
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.