Rock Ridge Lake Dam
Rock Ridge Lake Dam is an earth dam located in Morris County, New Jersey, built in 1949. It carries a Significant hazard potential classification and has a poor condition assessment.
About Rock Ridge Lake Dam
The primary purpose of Rock Ridge Lake Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Rock Ridge Community Club (private). It impounds the Denney Brook near Denville.
The dam stands 10 feet tall and stretches 235 feet across, creates a reservoir covering 17 acres, has a storage capacity of 174 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1949, the structure is well-established, with more than 75 years of service.
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 04/15/2025.
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Location
| State | New Jersey |
| County | Morris |
| Nearest City | Denville |
| River/Stream | Denney Brook |
| Coordinates | 40.91135, -74.46343 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 10 ft |
| Dam Height | 10 ft |
| Dam Length | 235 ft |
| Year Completed | 1949 (77 years old) |
Storage & Hydraulics
| NID Storage | 174 acre-ft |
| Normal Storage | 174 acre-ft |
| Surface Area | 17 acres |
| Drainage Area | 0 sq mi |
| Max Discharge | 330 cfs |
Ownership & Safety
| Purpose | Recreation |
| Owner | Rock Ridge Community Club |
| Owner Type | Private |
| Hazard Classification | Significant |
| Condition Assessment | Poor |
| Last Inspection | 04/15/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | NJ00178 |
| Federal ID | NJ00178 |
| More Info | State Dam Safety Program |