Cornwell is an earth dam located in Valley County, Montana, built in 1952. It carries a Significant hazard potential classification.
Dam profile
NID height · 23 ft23 ft tall and 400 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 Cornwell
The primary purpose of Cornwell is irrigation. The dam stores and diverts water for agricultural irrigation, supporting farming operations in the surrounding area. The dam is owned by Cornwell Ranch (private). It impounds the Wire Grass Coulee near Glasgow.
The dam stands 23 feet tall and stretches 400 feet across, has a maximum storage capacity of 423 acre-feet, and collects water from a drainage area of 2 square miles. Completed in 1952, 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 | Montana |
| County | Valley |
| Nearest City | Glasgow |
| River/Stream | Wire Grass Coulee |
| Coordinates | 48.37440, -106.71340 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 23 ft |
| Dam Height | 23 ft |
| Dam Length | 400 ft |
| Year Completed | 1952 (74 years old) |
Storage & Hydraulics
| NID Storage | 423 acre-ft |
| Max Storage | 423 acre-ft |
| Normal Storage | 238 acre-ft |
| Drainage Area | 2 sq mi |
| Max Discharge | 600 cfs |
Ownership & Safety
| Purpose | Irrigation |
| Owner | Cornwell Ranch |
| Owner Type | Private |
| Hazard Classification | Significant |
| Condition Assessment | Not assessed |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | MT00998 |
| Federal ID | MT00998 |
| More Info | State Dam Safety Program |