Manasquan Reservoir Dam
Manasquan Reservoir Dam is an earth dam located in Monmouth County, New Jersey, built in 1990. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Manasquan Reservoir Dam
The primary purpose of Manasquan Reservoir 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 New Jersey Water Supply Authority (state). It impounds the Timber Swamp Brook near Howell.
The dam stands 53 feet tall and stretches 4,840 feet across, creates a reservoir covering 770 acres, has a maximum storage capacity of 18,470 acre-feet, and collects water from a drainage area of 3 square miles. Completed in 1990, the structure is 36 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 10/22/2024.
At 53 feet, this dam is taller than 94% 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 | Monmouth |
| Nearest City | Howell |
| River/Stream | Timber Swamp Brook |
| Coordinates | 40.17935, -74.19350 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 53 ft |
| Dam Height | 53 ft |
| Dam Length | 4,840 ft |
| Year Completed | 1990 (36 years old) |
Storage & Hydraulics
| NID Storage | 18,470 acre-ft |
| Max Storage | 18,470 acre-ft |
| Normal Storage | 14,470 acre-ft |
| Surface Area | 770 acres |
| Drainage Area | 3 sq mi |
Ownership & Safety
| Purpose | Water Supply |
| Owner | New Jersey Water Supply Authority |
| Owner Type | State |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 10/22/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NJ00858 |
| Federal ID | NJ00858 |
| More Info | State Dam Safety Program |