Lake Grinnell Dam
Lake Grinnell Dam is an earth dam located in Sussex County, New Jersey, built in 1900. It carries a Significant hazard potential classification and has a poor condition assessment.
About Lake Grinnell Dam
The primary purpose of Lake Grinnell Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Lake Grinnell Homeowners Association (private). It impounds the Wallkill River-tr.
The dam stands 12 feet tall and stretches 195 feet across, creates a reservoir covering 46 acres, has a storage capacity of 150 acre-feet, and collects water from a drainage area of 2 square miles. Completed in 1900, 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 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 04/12/2024.
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Location
| State | New Jersey |
| County | Sussex |
| River/Stream | Wallkill River-tr |
| Coordinates | 41.10137, -74.63590 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 12 ft |
| Dam Height | 12 ft |
| Dam Length | 195 ft |
| Year Completed | 1900 (126 years old) |
Storage & Hydraulics
| NID Storage | 150 acre-ft |
| Normal Storage | 150 acre-ft |
| Surface Area | 46 acres |
| Drainage Area | 2 sq mi |
| Max Discharge | 30 cfs |
Ownership & Safety
| Purpose | Recreation |
| Owner | Lake Grinnell Homeowners Association |
| Owner Type | Private |
| Hazard Classification | Significant |
| Condition Assessment | Poor |
| Last Inspection | 04/12/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NJ00289 |
| Federal ID | NJ00289 |
| More Info | State Dam Safety Program |