Upper Glasston North Dam
Upper Glasston North Dam is an earth dam located in Sweet Grass County, Montana, built in 1912. It carries a High hazard potential classification and has a poor condition assessment.
About Upper Glasston North Dam
The primary purpose of Upper Glasston North Dam is irrigation. The dam stores and diverts water for agricultural irrigation, supporting farming operations in the surrounding area. The dam is owned by Sweetgrass Canal & Res Co (private). It impounds the Sweetgrass Canal Offstream near Greycliff.
The dam stands 20 feet tall and stretches 600 feet across, and has a maximum storage capacity of 1,805 acre-feet. Completed in 1912, the structure is over a century old.
This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated poor, meaning the dam has recognized safety deficiencies that require remediation to address risks. An emergency action plan is in place for this dam. The most recent inspection on record was 07/10/2021.
Living Downstream
If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Montana dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Montana |
| County | Sweet Grass |
| Nearest City | Greycliff |
| River/Stream | Sweetgrass Canal Offstream |
| Coordinates | 46.03900, -109.82625 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 20 ft |
| Dam Height | 20 ft |
| Dam Length | 600 ft |
| Year Completed | 1912 (114 years old) |
Storage & Hydraulics
| NID Storage | 1,805 acre-ft |
| Max Storage | 1,805 acre-ft |
| Normal Storage | 924 acre-ft |
Ownership & Safety
| Purpose | Irrigation |
| Owner | SWEETGRASS CANAL & RES CO |
| Owner Type | Private |
| Hazard Classification | High |
| Condition Assessment | Poor |
| Last Inspection | 07/10/2021 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | MT03267 |
| Federal ID | MT00380S001 |
| More Info | State Dam Safety Program |