Lower Silvis
Key Takeaway
Lower Silvis is classified as low hazard in Alaska. It was completed in 1954 and is 72 years old. Its primary use is hydroelectric.
Physical Details
| Dam Height | 32 ft (taller than 58.8% in AK) |
| Dam Length | 140 ft |
| Dam Type | Rockfill |
| Max Storage | 1.6K acre-ft |
| Normal Storage | 1.4K acre-ft |
| Surface Area | 68 acres |
| Drainage Area | 1 sq mi |
| Max Discharge | 7,900 cfs |
| Year Completed | 1954 (72 years old) |
| NID ID | AK00008 |
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
Local Government
Nearby Dams
Upper Silvis
Ketchikan Gateway Borough, AK
Low Hazard 60 ftWhitman Lake
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High Hazard 39 ftKetchikan Lakes
Ketchikan Gateway Borough, AK
High Hazard 34 ftFawn Lake Dam North
Ketchikan Gateway Borough, AK
Significant Hazard 15 ftLake Connell
Ketchikan Gateway Borough, AK
High Hazard 96 ftCarlanna Lake
Ketchikan Gateway Borough, AK
High Hazard 31 ftWard Cove Cannery Dam
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Low Hazard 25 ftFrequently Asked Questions
What is the hazard classification of Lower Silvis?
Lower 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 Lower Silvis?
Lower Silvis is owned by City of Ketchikan (Local Government). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.
When was Lower Silvis built?
Lower Silvis was completed in 1954, making it 72 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 Lower Silvis?
Lower 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 Lower Silvis?
Lower Silvis has a dam height of 32 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 Lower Silvis last inspected?
Lower Silvis was last inspected on August 7, 2019. Inspection dates indicate when a formal review occurred, not the results of that inspection.