Mamaroneck Reservoir Dam
Mamaroneck Reservoir Dam is a concrete dam located in Westchester County, New York, built in 1928. It carries a High hazard potential classification and has a poor condition assessment.
About Mamaroneck Reservoir Dam
The primary purpose of Mamaroneck Reservoir 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 Village Of Mamaroneck;westchester Joint Waterworks (local government). It impounds the Mamaroneck River near Mamaroneck.
The dam stands 19 feet tall and stretches 185 feet across, creates a reservoir covering 18 acres, has a maximum storage capacity of 241 acre-feet, and collects water from a drainage area of 15 square miles. Completed in 1928, the structure is well-established, with more than 75 years 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. 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 03/21/2024.
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 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 | Westchester |
| Nearest City | Mamaroneck |
| River/Stream | Mamaroneck River |
| Coordinates | 40.96806, -73.73889 |
Physical Characteristics
| Dam Type | Concrete |
| NID Height | 19 ft |
| Dam Height | 19 ft |
| Dam Length | 185 ft |
| Year Completed | 1928 (98 years old) |
Storage & Hydraulics
| NID Storage | 241 acre-ft |
| Max Storage | 241 acre-ft |
| Normal Storage | 18 acre-ft |
| Surface Area | 18 acres |
| Drainage Area | 15 sq mi |
| Max Discharge | 4,240 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | VILLAGE OF MAMARONECK;Westchester Joint Waterworks |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Poor |
| Last Inspection | 03/21/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NY00111 |
| Federal ID | NY00111 |
| More Info | State Dam Safety Program |