Mcnab Dam is a gravity dam located in Valley County, Montana, built in 2003. It carries a Low hazard potential classification and has a unsatisfactory condition assessment.
Dam profile
NID height · 39 ft39 ft tall and 396 ft long, taller than 85% 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 concrete gravity section and the water level is illustrative.
About Mcnab Dam
Mcnab Dam is a dam in Valley, Montana. The dam is owned by Doi BLM (federal).
The dam stands 39 feet tall and stretches 396 feet across, creates a reservoir covering 10 acres, and has a maximum storage capacity of 172 acre-feet. Completed in 2003, the structure is relatively new.
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 unsatisfactory, indicating serious safety deficiencies exist that require immediate attention or remedial action. The most recent inspection on record was 08/18/2016. That was over 10 years ago.
At 39 feet, this dam is taller than 85% of dams nationwide.
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Location
| State | Montana |
| County | Valley |
| Coordinates | 48.32476, -107.21286 |
Physical Characteristics
| Dam Type | Gravity |
| NID Height | 39 ft |
| Dam Length | 396 ft |
| Year Completed | 2003 (23 years old) |
Storage & Hydraulics
| NID Storage | 172 acre-ft |
| Max Storage | 172 acre-ft |
| Surface Area | 10 acres |
| Spillway Type | Controlled |
Ownership & Safety
| Owner | Doi BLM |
| Owner Type | Federal |
| Hazard Classification | Low |
| Condition Assessment | Unsatisfactory |
| Last Inspection | 08/18/2016 |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | MT03893 |
| Federal ID | MT03893 |
| More Info | State Dam Safety Program |