New Underwood is an earth dam located in Pennington County, South Dakota, built in 1946. It carries a Low hazard potential classification.
Dam profile
NID height · 22 ft22 ft tall and 1,000 ft long. 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 New Underwood
The primary purpose of New Underwood is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Gf&p (state). It impounds the Box Elder Creek-tr near New Underwood.
The dam stands 22 feet tall and stretches 1,000 feet across, creates a reservoir covering 59 acres, has a maximum storage capacity of 164 acre-feet, and collects water from a drainage area of 3 square miles. Completed in 1946, 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 04/19/2023.
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Location
| State | South Dakota |
| County | Pennington |
| Nearest City | New Underwood |
| River/Stream | Box Elder Creek-tr |
| Coordinates | 44.10533, -102.84076 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 22 ft |
| Dam Height | 22 ft |
| Dam Length | 1,000 ft |
| Year Completed | 1946 (80 years old) |
Storage & Hydraulics
| NID Storage | 164 acre-ft |
| Max Storage | 164 acre-ft |
| Normal Storage | 59 acre-ft |
| Surface Area | 59 acres |
| Drainage Area | 3 sq mi |
| Max Discharge | 380 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | Gf&p |
| Owner Type | State |
| Hazard Classification | Low |
| Condition Assessment | Not assessed |
| Last Inspection | 04/19/2023 |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | SD00034 |
| Federal ID | SD00034 |
| More Info | State Dam Safety Program |