Sully 2 is an earth dam located in Todd County, South Dakota, built in 1935. It carries a High hazard potential classification and has a satisfactory condition assessment.
Dam profile
NID height · 29 ft29 ft tall and 496 ft long, taller than 65% of U.S. dams with a recorded height. 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 Sully 2
The primary purpose of Sully 2 is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Bia (federal). It impounds the Oak Creek -tr near Okreek.
The dam stands 29 feet tall and stretches 496 feet across, creates a reservoir covering 18 acres, has a maximum storage capacity of 328 acre-feet, and collects water from a drainage area of 1 square miles. Completed in 1935, the structure is well-established, with more than 75 years of service.
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 04/20/2022.
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 Dakota 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 Dakota |
| County | Todd |
| Nearest City | Okreek |
| River/Stream | Oak Creek -tr |
| Coordinates | 43.36775, -100.40898 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 29 ft |
| Dam Height | 29 ft |
| Dam Length | 496 ft |
| Year Completed | 1935 (91 years old) |
Storage & Hydraulics
| NID Storage | 328 acre-ft |
| Max Storage | 328 acre-ft |
| Normal Storage | 279 acre-ft |
| Surface Area | 18 acres |
| Drainage Area | 1 sq mi |
| Max Discharge | 1,904 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | Bia |
| Owner Type | Federal |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 04/20/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | SD02562 |
| Federal ID | SD02562 |
| More Info | State Dam Safety Program |