Lake Dark Hollow Dam
Lake Dark Hollow Dam is an earth dam located in Westchester County, New York, built in 1913. It carries a Significant hazard potential classification and has a fair condition assessment.
About Lake Dark Hollow Dam
The primary purpose of Lake Dark Hollow 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 Dark Hollow Lake Association, Inc. (private). It impounds the Tr-pleasantville Cove near Thornwood.
The dam stands 28 feet tall and stretches 600 feet across, creates a reservoir covering 9 acres, has a maximum storage capacity of 116 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1913, the structure is over a century old.
This dam has a significant hazard potential classification, meaning that a failure could cause significant economic damage — flooding roads, bridges, or property downstream — but is not expected to result in loss of life. Its condition is rated fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. An emergency action plan is in place for this dam. The most recent inspection on record was 02/04/2025.
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Location
| State | New York |
| County | Westchester |
| Nearest City | Thornwood |
| River/Stream | Tr-pleasantville Cove |
| Coordinates | 41.14222, -73.74611 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 28 ft |
| Dam Height | 28 ft |
| Dam Length | 600 ft |
| Year Completed | 1913 (113 years old) |
Storage & Hydraulics
| NID Storage | 116 acre-ft |
| Max Storage | 116 acre-ft |
| Normal Storage | 61 acre-ft |
| Surface Area | 9 acres |
| Drainage Area | 0 sq mi |
| Max Discharge | 335 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Water Supply |
| Owner | DARK HOLLOW LAKE ASSOCIATION, INC. |
| Owner Type | Private |
| Hazard Classification | Significant |
| Condition Assessment | Fair |
| Last Inspection | 02/04/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NY00048 |
| Federal ID | NY00048 |
| More Info | State Dam Safety Program |