Onion River
Key Takeaway
Onion River is classified as high hazard in Wisconsin. It was completed in 1856 and is 170 years old. Its primary use is recreation. 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 | 15 ft (taller than 45% in WI) |
| Dam Length | 300 ft |
| Dam Type | Gravity |
| Max Storage | 200 acre-ft |
| Normal Storage | 100 acre-ft |
| Surface Area | 40 acres |
| Drainage Area | 22 sq mi |
| Max Discharge | 1,165 cfs |
| Year Completed | 1856 (170 years old) |
| NID ID | WI00313 |
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
Village of Waldo
Local Government
Nearby Dams
Hingham
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Low Hazard 14 ftFrequently Asked Questions
What is the hazard classification of Onion River?
Onion River 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 Onion River?
Onion River is owned by Village of Waldo (Local Government). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.
When was Onion River built?
Onion River was completed in 1856, making it 170 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 Onion River?
Onion River serves the following purposes: Recreation. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.
How tall is Onion River?
Onion River has a dam height of 15 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 Onion River last inspected?
Onion River was last inspected on August 27, 2020. Inspection dates indicate when a formal review occurred, not the results of that inspection.