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South Tongass Hwy over Tongass Avenue Viaduct

Ketchikan Gateway Borough, Alaska · rated Fair in the 2025 National Bridge Inventory

United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled August 20, 2026

South Tongass Hwy over Tongass Avenue Viaduct in Ketchikan Gateway Borough, Alaska, is rated in fair condition in the 2025 National Bridge Inventory (as of August 20, 2026).
Its lowest-rated component is the substructure, rated 5 (fair condition) on the 0-9 scale.
It was built in 1956, making it 69 years old at the 2025 inventory.
It carries about 14,564 vehicles a day (traffic count year 2018).
Its listed owner is the state highway agency.
It is one of 45 of the 107 inventoried bridges in Ketchikan Gateway Borough rated fair (42.1%); 12 (11.2%) are rated poor.
A fair rating means the lowest-rated major component scores 5 or 6 on FHWA's 0-9 scale: some deterioration or minor section loss, but the structure is sound. It is the middle class, not a warning.

Component ratings


Structure	Prestressed concrete tee beam
Length	about 1,727 ft
Location	Mile Point 1.3
NBI structure number	0997
Condition class	Fair

Source: FHWA National Bridge Inventory, 2025 data as reported by the Alaska department of transportation.

Bridge	Built	Vehicles/day	Condition
South Tongass Hwy over Water St Viaduct	1955	14,046	Poor
South Tongass Hwy over Hoadley Creek	1957	11,900	Poor
North Tongass Hwy over Carlanna Creek	1973	9,210	Fair
South Tongass Hwy over Front Street Viaduct	1969	8,330	Fair
South Tongass Hwy over Ketchikan Creek	1944	6,850	Fair
South Tongass Hwy over Front and Mill St Viad	1973	6,830	Good