Upper Silvis
Key Takeaway
Upper Silvis is classified as low hazard in Alaska. It was completed in 1968 and is 58 years old. Its primary use is hydroelectric.
Physical Details
| Dam Height | 60 ft (taller than 77.6% in AK) |
| Dam Length | 135 ft |
| Dam Type | Rockfill |
| Max Storage | 38.0K acre-ft |
| Normal Storage | 22.0K acre-ft |
| Surface Area | 300 acres |
| Drainage Area | 3 sq mi |
| Max Discharge | 6,000 cfs |
| Year Completed | 1968 (58 years old) |
| NID ID | AK00007 |
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
City of Ketchikan
Public Utility
Nearby Dams
Lower Silvis
Ketchikan Gateway Borough, AK
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High Hazard 39 ftKetchikan Lakes
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High Hazard 34 ftFawn Lake Dam North
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Significant Hazard 15 ftLake Connell
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High Hazard 96 ftCarlanna Lake
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High Hazard 31 ftWard Cove Cannery Dam
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Low Hazard 25 ftFrequently Asked Questions
What is the hazard classification of Upper Silvis?
Upper Silvis 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 Upper Silvis?
Upper Silvis is owned by City of Ketchikan (Public Utility). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.
When was Upper Silvis built?
Upper Silvis was completed in 1968, making it 58 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 Upper Silvis?
Upper Silvis 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 Upper Silvis?
Upper Silvis has a dam height of 60 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 Upper Silvis last inspected?
Upper Silvis was last inspected on August 7, 2019. Inspection dates indicate when a formal review occurred, not the results of that inspection.