Upper Silvis
Upper Silvis is a rockfill dam located in Ketchikan Gateway Borough, Alaska, built in 1968. It carries a Low hazard potential classification and has a satisfactory condition assessment.
About Upper Silvis
The primary purpose of Upper Silvis is hydroelectric. The dam generates hydroelectric power by channeling water through turbines, converting the energy of flowing water into electricity. The dam is owned by City Of Ketchikan (public utility). It impounds the Beaver Falls Creek, George Inl.
The dam stands 60 feet tall and stretches 135 feet across, creates a reservoir covering 300 acres, has a maximum storage capacity of 38,000 acre-feet, and collects water from a drainage area of 3 square miles. Completed in 1968, the structure is well into its service life at over 50 years old.
This dam has a low hazard potential classification, meaning that failure would cause minimal damage, limited primarily to the dam owner's property, with no expected loss of life. Its condition is rated satisfactory, indicating no existing or potential dam safety deficiencies are recognized. The most recent inspection on record was 08/07/2019.
At 60 feet, this dam is taller than 95% of all dams in the United States.
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Location
| State | Alaska |
| County | Ketchikan Gateway Borough |
| Nearest City | None |
| River/Stream | Beaver Falls Creek, George Inl |
| Coordinates | 55.37996, -131.51893 |
Physical Characteristics
| Dam Type | Rockfill |
| NID Height | 60 ft |
| Dam Height | 60 ft |
| Dam Length | 135 ft |
| Year Completed | 1968 (58 years old) |
Storage & Hydraulics
| NID Storage | 38,000 acre-ft |
| Max Storage | 38,000 acre-ft |
| Normal Storage | 22,000 acre-ft |
| Surface Area | 300 acres |
| Drainage Area | 3 sq mi |
| Max Discharge | 6,000 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner | City of Ketchikan |
| Owner Type | Public Utility |
| Hazard Classification | Low |
| Condition Assessment | Satisfactory |
| Last Inspection | 08/07/2019 |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | AK00007 |
| Federal ID | AK00007 |
| More Info | State Dam Safety Program |