Lake Tappan Dam Reservoir Report
Nearby: Lake Tappan Dike Mill Pond Dam
Last Updated: December 11, 2025
Lake Tappan Dam, located in Old Tappan, New Jersey, is a significant earth dam that was completed in 1966 for the primary purpose of water supply.
°F
°F
mph
Wind
%
Humidity
Summary
With a height of 34 feet and a length of 590 feet, the dam has a storage capacity of 13,600 acre-feet and a surface area of 560 acres. It is situated on the Hackensack River in Bergen County and is owned and regulated by private entities, with oversight from the New Jersey Department of Environmental Protection.
Despite being classified as having a high hazard potential, the dam's condition has been assessed as satisfactory during its last inspection in June 2021. The emergency action plan for the dam was last revised in February 2022, indicating preparedness for potential risks associated with its operation. The dam's drainage area covers 49.2 square miles, with a maximum discharge capacity of 27,000 cubic feet per second, highlighting its critical role in flood control and water resource management in the region.
Lake Tappan Dam serves as a vital infrastructure for water supply and flood control in the area, demonstrating the intersection of water resource management and climate resilience. Its strategic location on the Hackensack River, coupled with its storage capacity and regulatory oversight, underscores its importance in ensuring water security and mitigating potential risks associated with its operation. As climate change impacts continue to pose challenges to water resources, the maintenance and monitoring of dams like Lake Tappan Dam become increasingly crucial for sustainable water management in the region.
Year Completed |
1966 |
Dam Length |
590 |
Dam Height |
34 |
River Or Stream |
Hackensack River |
Primary Dam Type |
Earth |
Surface Area |
560 |
Drainage Area |
49.2 |
Nid Storage |
13600 |
Hazard Potential |
High |
Nid Height |
34 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Lake Tappan Dam
Stone Point Park
Wood Dale County Park
Schmidt Property
Pondside Park
Hillsdale Memorial Park