First Avenue South Bridge

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First Avenue South Bridge
Lower Duwamish River.jpg
The original First Avenue South Bridge over the Duwamish, before the construction of the southbound span
Coordinates47°32′32″N 122°20′04″W / 47.54222°N 122.33444°W / 47.54222; -122.33444Coordinates: 47°32′32″N 122°20′04″W / 47.54222°N 122.33444°W / 47.54222; -122.33444
Carries SR 99
CrossesDuwamish River
LocaleSeattle, Washington
DesignBascule bridge
Total length3,010 ft (920 m) (northbound)[1]
2,895 ft (882 m) (southbound)[1]
Opened1956 (northbound)
1997 (southbound)

The First Avenue South Bridge is a pair of double-leaf bascule bridges built between 1956 and 1998 that carry State Route 99 over the Duwamish River about three miles (5 km) south of downtown Seattle, Washington.

The northbound span was built in 1956 to connect the industrial areas northeast of the Duwamish to the residential neighborhoods to the south and southwest. Between 1996 and 1998, the drawspan was retrofitted and the approaches completely demolished and rebuilt. The southbound span opened in February 1997 and carried traffic in both directions for two years while the northbound span was rebuilt.[2]

In 2001, the southbound span was damaged by the Nisqually earthquake, knocking its piers 3 inches out of alignment, and was closed briefly for repairs.[3]

From the original construction to February 1995 when the retrofit began, the First Ave S bridge had the highest motor vehicle accident rate in Washington State.[citation needed]


  1. ^ a b "Bridge List" (PDF). Washington State Department of Transportation. May 2010. Retrieved 11 April 2011.
  2. ^ Beers, Carole (February 2, 1997). "New Duwamish span opens while old one is fixed". The Seattle Times. p. B1.
  3. ^ "First Avenue bridge to close this weekend for repairs". Seattle Post-Intelligencer. 2001-03-08.[dead link]


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