Offerdahl-Johnson Dam
Key Takeaway
Offerdahl-Johnson Dam is classified as low hazard in Montana. It was completed in 1980 and is 46 years old. Its primary use is irrigation.
Physical Details
| Dam Height | 17 ft (taller than 34.9% in MT) |
| Dam Length | 1,840 ft |
| Dam Type | Earth |
| Max Storage | 900 acre-ft |
| Normal Storage | 900 acre-ft |
| Surface Area | 132 acres |
| Year Completed | 1980 (46 years old) |
| NID ID | MT03798 |
Safety Information
No probable loss of human life and low economic/environmental losses expected.
Hazard potential describes downstream consequences of failure, not the dam's current condition. What does this mean?
Ownership
AETNA INSURANCE COMPANY
Private
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Low Hazard 27 ftFrequently Asked Questions
What is the hazard classification of Offerdahl-Johnson Dam?
Offerdahl-Johnson Dam is classified as Low Hazard. No probable loss of human life and low economic/environmental losses expected. This classification refers to the potential downstream consequences of a failure, not the dam's current structural condition.
Who owns and operates Offerdahl-Johnson Dam?
Offerdahl-Johnson Dam is owned by AETNA INSURANCE COMPANY (Private). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.
When was Offerdahl-Johnson Dam built?
Offerdahl-Johnson Dam was completed in 1980, making it 46 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 Offerdahl-Johnson Dam?
Offerdahl-Johnson Dam serves the following purposes: Irrigation. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.
How tall is Offerdahl-Johnson Dam?
Offerdahl-Johnson Dam has a dam height of 17 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.