Grandmother
Key Takeaway
Grandmother is classified as high hazard in Wisconsin. It was completed in 1923 and is 103 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 | 39 ft (taller than 91.9% in WI) |
| Dam Length | 724 ft |
| Dam Type | Gravity |
| Max Storage | 1.9K acre-ft |
| Normal Storage | 1.9K acre-ft |
| Surface Area | 758 acres |
| Drainage Area | 2,269 sq mi |
| Max Discharge | 61,500 cfs |
| Year Completed | 1923 (103 years old) |
| NID ID | WI00747 |
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
PCA Hydro Inc.
Private
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What is the hazard classification of Grandmother?
Grandmother 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 Grandmother?
Grandmother is owned by PCA Hydro Inc. (Private). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.
When was Grandmother built?
Grandmother was completed in 1923, making it 103 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 Grandmother?
Grandmother 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 Grandmother?
Grandmother has a dam height of 39 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 Grandmother last inspected?
Grandmother was last inspected on September 13, 2022. Inspection dates indicate when a formal review occurred, not the results of that inspection.