Ninety Nine Islands
Ninety Nine Islands is a concrete dam located in Cherokee County, South Carolina, built in 1909. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Ninety Nine Islands
The primary purpose of Ninety Nine Islands is hydroelectric. The dam generates hydroelectric power by channeling water through turbines, converting the energy of flowing water into electricity. The dam is owned by Duke Energy (public utility). It impounds the Broad near Lockhart.
The dam stands 72 feet tall and stretches 1,568 feet across, creates a reservoir covering 350 acres, has a maximum storage capacity of 2,300 acre-feet, and collects water from a drainage area of 1,550 square miles. Completed in 1909, the structure is over a century old.
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 satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 03/28/2022.
At 72 feet, this dam is taller than 96% of all dams in the United States.
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 South Carolina 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 | South Carolina |
| County | Cherokee |
| Nearest City | Lockhart |
| River/Stream | Broad |
| Coordinates | 35.03077, -81.49458 |
Physical Characteristics
| Dam Type | Concrete |
| NID Height | 72 ft |
| Dam Height | 72 ft |
| Dam Length | 1,568 ft |
| Year Completed | 1909 (117 years old) |
Storage & Hydraulics
| NID Storage | 2,300 acre-ft |
| Max Storage | 2,300 acre-ft |
| Normal Storage | 2,300 acre-ft |
| Surface Area | 350 acres |
| Drainage Area | 1,550 sq mi |
| Max Discharge | 145,000 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner | Duke Energy |
| Owner Type | Public Utility |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 03/28/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | SC01074 |
| Federal ID | SC01074 |
| More Info | State Dam Safety Program |