John Ball Reservoir is an earth dam located in McCone County, Montana, built in 1935. It carries a Significant hazard potential classification.
Dam profile
NID height · 16 ft16 ft tall and 360 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 John Ball Reservoir
The primary purpose of John Ball Reservoir 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 Lyle E Nelson (private). It impounds the Tr-south Fork Rock Creek near No Town.
The dam stands 16 feet tall and stretches 360 feet across, has a maximum storage capacity of 145 acre-feet, and collects water from a drainage area of 1 square miles. Completed in 1935, the structure is well-established, with more than 75 years of service.
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 | Montana |
| County | McCone |
| Nearest City | No Town |
| River/Stream | Tr-south Fork Rock Creek |
| Coordinates | 47.72070, -106.13850 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 16 ft |
| Dam Height | 16 ft |
| Dam Length | 360 ft |
| Year Completed | 1935 (91 years old) |
Storage & Hydraulics
| NID Storage | 145 acre-ft |
| Max Storage | 145 acre-ft |
| Normal Storage | 61 acre-ft |
| Drainage Area | 1 sq mi |
| Max Discharge | 1,000 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Fire Protection, Stock, Or Small Fish Pond |
| Owner | Lyle E Nelson |
| Owner Type | Private |
| Hazard Classification | Significant |
| Condition Assessment | Not assessed |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | MT00482 |
| Federal ID | MT00482 |
| More Info | State Dam Safety Program |