Lake Deforest Dam
Lake Deforest Dam is an earth dam located in Rockland County, New York, built in 1956. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Lake Deforest Dam
The primary purpose of Lake Deforest 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 Veolia Water New York, Inc. (public utility). It impounds the Hackensack River near West Nyack.
The dam stands 40 feet tall and stretches 1,330 feet across, creates a reservoir covering 900 acres, has a maximum storage capacity of 36,362 acre-feet, and collects water from a drainage area of 26 square miles. Completed in 1956, the structure is well into its service life at over 50 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 10/10/2024.
At 40 feet, this dam is taller than 87% 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 | Rockland |
| Nearest City | West Nyack |
| River/Stream | Hackensack River |
| Coordinates | 41.10620, -73.96746 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 40 ft |
| Dam Height | 40 ft |
| Dam Length | 1,330 ft |
| Year Completed | 1956 (70 years old) |
Storage & Hydraulics
| NID Storage | 36,362 acre-ft |
| Max Storage | 36,362 acre-ft |
| Normal Storage | 17,250 acre-ft |
| Surface Area | 900 acres |
| Drainage Area | 26 sq mi |
| Spillway Type | Controlled |
Ownership & Safety
| Purpose | Water Supply |
| Owner | Veolia Water NEW YORK, Inc. |
| Owner Type | Public Utility |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 10/10/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NY00095 |
| Federal ID | NY00095 |
| More Info | State Dam Safety Program |