Whidby Structure 20
Whidby Structure 20 is an earth dam located in Jackson County, South Dakota, built in 1966. It carries a Significant hazard potential classification.
About Whidby Structure 20
The primary purpose of Whidby Structure 20 is irrigation. The dam stores and diverts water for agricultural irrigation, supporting farming operations in the surrounding area. The dam is owned by Mitchell-slovek Ranch Llp (private). It impounds the Tr-white River.
The dam stands 24 feet tall and stretches 400 feet across, and has a maximum storage capacity of 128 acre-feet. Completed in 1966, the structure is well into its service life at over 50 years 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.
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Location
| State | South Dakota |
| County | Jackson |
| River/Stream | Tr-white River |
| Coordinates | 43.76820, -101.54580 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 24 ft |
| Dam Height | 24 ft |
| Dam Length | 400 ft |
| Year Completed | 1966 (60 years old) |
Storage & Hydraulics
| NID Storage | 128 acre-ft |
| Max Storage | 128 acre-ft |
| Normal Storage | 85 acre-ft |
| Max Discharge | 1,050 cfs |
Ownership & Safety
| Purpose | Irrigation |
| Owner | Mitchell-Slovek Ranch LLP |
| Owner Type | Private |
| Hazard Classification | Significant |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | SD02008 |
| Federal ID | SD02008 |
| More Info | State Dam Safety Program |