Ryan
Key Takeaway
Ryan is classified as high hazard in Montana. It was completed in 1915 and is 111 years old. Its primary use is hydroelectric. High hazard means loss of life is likely if the dam fails — it does not indicate the dam's current condition. Learn more.
Physical Details
| Dam Height | 61 ft (taller than 97.8% in MT) |
| Dam Length | 1,465 ft |
| Dam Type | Gravity |
| Max Storage | 3.6K acre-ft |
| Normal Storage | 3.7K acre-ft |
| Surface Area | 168 acres |
| Drainage Area | 23,080 sq mi |
| Max Discharge | 188,000 cfs |
| Year Completed | 1915 (111 years old) |
| NID ID | MT00555 |
Safety Information
Loss of human life is likely if the dam fails.
Hazard potential describes downstream consequences of failure, not the dam's current condition. What does this mean?
Ownership
NorthWestern Energy
Private
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Low Hazard 36 ftFrequently Asked Questions
What is the hazard classification of Ryan?
Ryan is classified as High Hazard. Loss of human life is likely if the dam fails. This classification refers to the potential downstream consequences of a failure, not the dam's current structural condition.
Who owns and operates Ryan?
Ryan is owned by NorthWestern Energy (Private). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.
When was Ryan built?
Ryan was completed in 1915, making it 111 years old. Many U.S. dams were built between the 1930s and 1970s during a period of major infrastructure investment.
What is the primary purpose of Ryan?
Ryan serves the following purposes: Hydroelectric. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.
How tall is Ryan?
Ryan has a dam height of 61 ft. Dam height is measured from the natural streambed at the downstream toe to the top of the dam, and may differ from the visible height.
When was Ryan last inspected?
Ryan was last inspected on July 18, 2022. Inspection dates indicate when a formal review occurred, not the results of that inspection.