Lake Tappan Dam is an earth dam located in Bergen County, New Jersey, built in 1966. It carries a High hazard potential classification and has a satisfactory condition assessment.
Dam profile
NID height · 34 ft34 ft tall and 590 ft long, taller than 78% of U.S. dams with a recorded height. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic embankment section and the water level is illustrative.
About Lake Tappan Dam
The primary purpose of Lake Tappan Dam is water supply. The dam stores water for municipal, industrial, or agricultural use, helping ensure a reliable supply for the surrounding area. The dam is owned by Suez Water New Jersey, Inc. (private). It impounds the Hackensack River near Old Tappan.
The dam stands 34 feet tall and stretches 590 feet across, creates a reservoir covering 560 acres, has a maximum storage capacity of 13,600 acre-feet, and collects water from a drainage area of 49 square miles. Completed in 1966, the structure is well into its service life at over 50 years old.
This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 12/06/2024.
At 34 feet, this dam is taller than 78% of dams nationwide.
Living Downstream
If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The New Jersey dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | New Jersey |
| County | Bergen |
| Nearest City | Old Tappan |
| River/Stream | Hackensack River |
| Coordinates | 41.01812, -74.00115 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 34 ft |
| Dam Height | 34 ft |
| Dam Length | 590 ft |
| Year Completed | 1966 (60 years old) |
Storage & Hydraulics
| NID Storage | 13,600 acre-ft |
| Max Storage | 13,600 acre-ft |
| Normal Storage | 11,815 acre-ft |
| Surface Area | 560 acres |
| Drainage Area | 49 sq mi |
| Max Discharge | 27,000 cfs |
Ownership & Safety
| Purpose | Water Supply |
| Owner | Suez Water New Jersey, Inc. |
| Owner Type | Private |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 12/06/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NJ00246 |
| Federal ID | NJ00246 |
| More Info | State Dam Safety Program |