Post Brook Dam
Post Brook Dam is a concrete dam located in Passaic County, New Jersey, built in 1923. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Post Brook Dam
The primary purpose of Post Brook Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Lake Iosco (private). It impounds the Post Brook.
The dam stands 15 feet tall and stretches 316 feet across, creates a reservoir covering 73 acres, has a storage capacity of 990 acre-feet, and collects water from a drainage area of 3 square miles. Completed in 1923, the structure is over a century 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 08/31/2023.
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 | Passaic |
| River/Stream | Post Brook |
| Coordinates | 41.02483, -74.32000 |
Physical Characteristics
| Dam Type | Concrete |
| NID Height | 15 ft |
| Dam Height | 15 ft |
| Dam Length | 316 ft |
| Year Completed | 1923 (103 years old) |
Storage & Hydraulics
| NID Storage | 990 acre-ft |
| Normal Storage | 990 acre-ft |
| Surface Area | 73 acres |
| Drainage Area | 3 sq mi |
| Max Discharge | 19 cfs |
Ownership & Safety
| Purpose | Recreation |
| Owner | Lake Iosco |
| Owner Type | Private |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 08/31/2023 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NJ00220 |
| Federal ID | NJ00220 |
| More Info | State Dam Safety Program |