Ethan
Ethan is an earth dam located in Hanson County, South Dakota, built in 1936. It carries a Low hazard potential classification.
About Ethan
The primary purpose of Ethan is flood risk reduction. The dam is designed to control downstream flooding by temporarily storing excess water during storms and releasing it at a controlled rate. The dam is owned by Gf&p (state). It impounds the Twelve Mile Creek.
The dam stands 15 feet tall and stretches 750 feet across, and has a maximum storage capacity of 402 acre-feet. Completed in 1936, the structure is well-established, with more than 75 years of service.
This dam has a low hazard potential classification, meaning that failure would cause minimal damage, limited primarily to the dam owner's property, with no expected loss of life. The most recent inspection on record was 10/04/2022.
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Location
| State | South Dakota |
| County | Hanson |
| Nearest City | None |
| River/Stream | Twelve Mile Creek |
| Coordinates | 43.54515, -97.94285 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 15 ft |
| Dam Height | 15 ft |
| Dam Length | 750 ft |
| Year Completed | 1936 (90 years old) |
Storage & Hydraulics
| NID Storage | 402 acre-ft |
| Max Storage | 402 acre-ft |
| Normal Storage | 210 acre-ft |
| Max Discharge | 1,370 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | GF&P |
| Owner Type | State |
| Hazard Classification | Low |
| Last Inspection | 10/04/2022 |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | SD00022 |
| Federal ID | SD00022 |
| More Info | State Dam Safety Program |