Lefferts Grist Mill Dam is an earth dam located in Suffolk County, New York, built in 1800. It carries a Low hazard potential classification.
Dam profile
NID height · 8 ft8 ft tall and 730 ft long. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic embankment section and the water level is illustrative.
About Lefferts Grist Mill Dam
The primary purpose of Lefferts Grist Mill Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Nature Conservancy Inc (private). It impounds the Tr-huntington Harbor.
The dam stands 8 feet tall and stretches 730 feet across, creates a reservoir covering 15 acres, and has a maximum storage capacity of 54 acre-feet. Completed in 1800, the structure is one of the older dams in the region, with over a century and a half of service.
This dam has a low hazard potential classification, meaning that failure would cause minimal damage, limited primarily to the dam owner's property, with no expected loss of life. The most recent inspection on record was 05/05/2009. That was over 17 years ago.
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Location
| State | New York |
| County | Suffolk |
| Nearest City | None |
| River/Stream | Tr-huntington Harbor |
| Coordinates | 40.90000, -73.44500 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 8 ft |
| Dam Height | 8 ft |
| Dam Length | 730 ft |
| Year Completed | 1800 (226 years old) |
Storage & Hydraulics
| NID Storage | 54 acre-ft |
| Max Storage | 54 acre-ft |
| Normal Storage | 27 acre-ft |
| Surface Area | 15 acres |
| Max Discharge | 360 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | Nature Conservancy Inc |
| Owner Type | Private |
| Hazard Classification | Low |
| Condition Assessment | Not assessed |
| Last Inspection | 05/05/2009 |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | NY01502 |
| Federal ID | NY01502 |
| More Info | State Dam Safety Program |