Lake Hopatcong Dam
Lake Hopatcong Dam is a concrete dam located in Morris County, New Jersey, built in 1925. It carries a High hazard potential classification and has a poor condition assessment.
About Lake Hopatcong Dam
The primary purpose of Lake Hopatcong Dam is flood risk reduction. The dam is designed to control downstream flooding by temporarily storing excess water during storms and releasing it at a controlled rate. The dam is owned by Division Of Parks And Forestry (state). It impounds the Musconetcong River.
The dam stands 17 feet tall and stretches 271 feet across, creates a reservoir covering 2,474 acres, has a storage capacity of 48,209 acre-feet, and collects water from a drainage area of 25 square miles. Completed in 1925, 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 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 08/28/2024.
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 | Morris |
| River/Stream | Musconetcong River |
| Coordinates | 40.91767, -74.66418 |
Physical Characteristics
| Dam Type | Concrete |
| NID Height | 17 ft |
| Dam Height | 17 ft |
| Dam Length | 271 ft |
| Year Completed | 1925 (101 years old) |
Storage & Hydraulics
| NID Storage | 48,209 acre-ft |
| Normal Storage | 48,209 acre-ft |
| Surface Area | 2,474 acres |
| Drainage Area | 25 sq mi |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | Division of Parks and Forestry |
| Owner Type | State |
| Hazard Classification | High |
| Condition Assessment | Poor |
| Last Inspection | 08/28/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NJ00327 |
| Federal ID | NJ00327 |
| More Info | State Dam Safety Program |