Sly Number 1 is an earth dam located in Charles Mix County, South Dakota, built in 1961. It carries a Significant hazard potential classification.
Dam profile
NID height · 25 ft25 ft tall and 280 ft long, taller than 50% 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 Sly Number 1
The primary purpose of Sly Number 1 is fire protection, stock, or small fish pond. The dam maintains a small impoundment used for fire suppression, livestock watering, or as a fish pond. The dam is owned by John R Cattle Co Inc (private). It impounds the Platte Creek-tr near None in Flood Plain.
The dam stands 25 feet tall and stretches 280 feet across, and has a maximum storage capacity of 18 acre-feet. Completed in 1961, 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 | Charles Mix |
| Nearest City | None in Flood Plain |
| River/Stream | Platte Creek-tr |
| Coordinates | 43.46134, -98.80347 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 25 ft |
| Dam Height | 25 ft |
| Dam Length | 280 ft |
| Year Completed | 1961 (65 years old) |
Storage & Hydraulics
| NID Storage | 18 acre-ft |
| Max Storage | 18 acre-ft |
| Normal Storage | 8 acre-ft |
| Max Discharge | 900 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Fire Protection, Stock, Or Small Fish Pond |
| Owner | John R Cattle Co Inc |
| Owner Type | Private |
| Hazard Classification | Significant |
| Condition Assessment | Not assessed |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | SD00224 |
| Federal ID | SD00224 |
| More Info | State Dam Safety Program |