Mcninch No. 1 is an earth dam located in Sublette County, Wyoming, built in 1947. It carries a Low hazard potential classification and has a poor condition assessment.
Dam profile
NID height · 33 ft33 ft tall and 1,150 ft long, taller than 76% 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 Mcninch No. 1
The primary purpose of Mcninch No. 1 is irrigation. The dam stores and diverts water for agricultural irrigation, supporting farming operations in the surrounding area. The dam is owned by Tf Land & Cattle LLC (private). It impounds the Beaver Creek Offstream near Big Piney.
The dam stands 33 feet tall and stretches 1,150 feet across, creates a reservoir covering 107 acres, has a maximum storage capacity of 1,620 acre-feet, and collects water from a drainage area of 1 square miles. Completed in 1947, 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 poor, meaning the dam has recognized safety deficiencies that require remediation to address risks. The most recent inspection on record was 06/06/2025.
At 33 feet, this dam is taller than 76% of dams nationwide.
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Location
| State | Wyoming |
| County | Sublette |
| Nearest City | Big Piney |
| River/Stream | Beaver Creek Offstream |
| Coordinates | 42.59900, -110.25190 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 33 ft |
| Dam Height | 33 ft |
| Dam Length | 1,150 ft |
| Year Completed | 1947 (79 years old) |
Storage & Hydraulics
| NID Storage | 1,620 acre-ft |
| Max Storage | 1,620 acre-ft |
| Normal Storage | 1,086 acre-ft |
| Surface Area | 107 acres |
| Drainage Area | 1 sq mi |
| Max Discharge | 21 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Irrigation |
| Owner | Tf Land & Cattle LLC |
| Owner Type | Private |
| Hazard Classification | Low |
| Condition Assessment | Poor |
| Last Inspection | 06/06/2025 |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | WY01273 |
| Federal ID | WY01273 |
| More Info | State Dam Safety Program |