Black Hills Power & Light First Enlargement is an earth dam located in Weston County, Wyoming, built in 1940. It carries a Low hazard potential classification and has a fair condition assessment.
Dam profile
NID height · 27 ft27 ft tall and 700 ft long, taller than 59% 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 Black Hills Power & Light First Enlargement
Black Hills Power & Light First Enlargement is a dam in Weston, Wyoming. The dam is owned by Black Hills Power and Light (public utility). It impounds the East Branch Poison Creek near Osage.
The dam stands 27 feet tall and stretches 700 feet across, creates a reservoir covering 30 acres, and has a storage capacity of 195 acre-feet. Completed in 1940, 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. Its condition is rated fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. The most recent inspection on record was 04/29/2021.
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Location
| State | Wyoming |
| County | Weston |
| Nearest City | Osage |
| River/Stream | East Branch Poison Creek |
| Coordinates | 43.97280, -104.40780 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 27 ft |
| Dam Height | 27 ft |
| Dam Length | 700 ft |
| Year Completed | 1940 (86 years old) |
Storage & Hydraulics
| NID Storage | 195 acre-ft |
| Normal Storage | 195 acre-ft |
| Surface Area | 30 acres |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Other |
| Owner | Black Hills Power and Light |
| Owner Type | Public Utility |
| Hazard Classification | Low |
| Condition Assessment | Fair |
| Last Inspection | 04/29/2021 |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | WY01520 |
| Federal ID | WY01520 |
| More Info | State Dam Safety Program |