North Lake B Dam
North Lake B Dam is an earth dam located in Herkimer County, New York, built in 1850. It carries a High hazard potential classification.
About North Lake B Dam
The primary purpose of North Lake B Dam is navigation. The dam maintains water levels sufficient for boat and barge traffic, supporting commercial or recreational navigation on the waterway. The dam is owned by New York State Canal Corporation (state). It impounds the Tr-black River near Atwell.
The dam stands 35 feet tall and stretches 575 feet across, creates a reservoir covering 442 acres, and has a maximum storage capacity of 6,190 acre-feet. Completed in 1850, the structure is one of the older dams in the region, with over a century and a half 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. An emergency action plan is in place for this dam. The most recent inspection on record was 04/10/2025.
At 35 feet, this dam is taller than 82% 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 York 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 York |
| County | Herkimer |
| Nearest City | Atwell |
| River/Stream | Tr-black River |
| Coordinates | 43.52333, -74.94333 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 35 ft |
| Dam Height | 35 ft |
| Dam Length | 575 ft |
| Year Completed | 1850 (176 years old) |
Storage & Hydraulics
| NID Storage | 6,190 acre-ft |
| Max Storage | 6,190 acre-ft |
| Normal Storage | 5,480 acre-ft |
| Surface Area | 442 acres |
| Max Discharge | 5,590 cfs |
| Spillway Type | None |
Ownership & Safety
| Purpose | Navigation |
| Owner | New York State Canal Corporation |
| Owner Type | State |
| Hazard Classification | High |
| Condition Assessment | Not Rated |
| Last Inspection | 04/10/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NY00326 |
| Federal ID | NY00326 |
| More Info | State Dam Safety Program |