Lake Lefferts Dam is an earth dam located in Monmouth County, New Jersey, built in 1928. It carries a High hazard potential classification and has a poor condition assessment.
Dam profile
NID height · 16 ft16 ft tall and 430 ft long. 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 Lefferts Dam
The primary purpose of Lake Lefferts Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Borough of Matawan (local government). It impounds the Matawan Creek near Keyport.
The dam stands 16 feet tall and stretches 430 feet across, creates a reservoir covering 65 acres, has a maximum storage capacity of 796 acre-feet, and collects water from a drainage area of 6 square miles. Completed in 1928, the structure is well-established, with more than 75 years of service.
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 poor, meaning the dam has recognized safety deficiencies that require remediation to address risks. An emergency action plan is in place for this dam. The most recent inspection on record was 11/27/2024.
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 | Monmouth |
| Nearest City | Keyport |
| River/Stream | Matawan Creek |
| Coordinates | 40.41563, -74.23230 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 16 ft |
| Dam Height | 16 ft |
| Dam Length | 430 ft |
| Year Completed | 1928 (98 years old) |
Storage & Hydraulics
| NID Storage | 796 acre-ft |
| Max Storage | 796 acre-ft |
| Normal Storage | 650 acre-ft |
| Surface Area | 65 acres |
| Drainage Area | 6 sq mi |
| Max Discharge | 260 cfs |
Ownership & Safety
| Purpose | Recreation |
| Owner | Borough of Matawan |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Poor |
| Last Inspection | 11/27/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NJ00089 |
| Federal ID | NJ00089 |
| More Info | State Dam Safety Program |