Mystic Lake
Key Takeaway
Mystic Lake is classified as high hazard in Montana. It was completed in 1927 and is 99 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 | 45 ft (taller than 96% in MT) |
| Dam Length | 368 ft |
| Dam Type | Arch |
| Max Storage | 21.0K acre-ft |
| Normal Storage | 20.8K acre-ft |
| Surface Area | 446 acres |
| Drainage Area | 45 sq mi |
| Max Discharge | 30,000 cfs |
| Year Completed | 1927 (99 years old) |
| NID ID | MT00562 |
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
Nearby Dams
Frequently Asked Questions
What is the hazard classification of Mystic Lake?
Mystic Lake 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 Mystic Lake?
Mystic Lake is owned by NorthWestern Energy (Private). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.
When was Mystic Lake built?
Mystic Lake was completed in 1927, making it 99 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 Mystic Lake?
Mystic Lake serves the following purposes: Hydroelectric, Recreation. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.
How tall is Mystic Lake?
Mystic Lake has a dam height of 45 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 Mystic Lake last inspected?
Mystic Lake was last inspected on September 30, 2020. Inspection dates indicate when a formal review occurred, not the results of that inspection.