Alaskan Way Viaduct

This article is about the existing bridge. For its replacement, see Alaskan Way Viaduct replacement tunnel.

Alaskan Way Viaduct
The Alaskan Way Viaduct, looking southeast
Carries	SR 99
Locale	Downtown Seattle, USA
Material	Concrete
Construction end	April 4, 1953
Daily traffic	110,000 cars per day

The Alaskan Way Viaduct, looking southeast

The Alaskan Way Viaduct seen from Elliott Bay

The Alaskan Way Viaduct, completed on April 4, 1953, is a double-decked elevated section of State Route 99 that runs along the Elliott Bay waterfront in the industrial district and downtown of Seattle. It is the smaller of the two major north–south traffic corridors through Seattle (the other being Interstate 5), carrying up to 110,000 vehicles per day. The viaduct runs above the surface street, Alaskan Way, from S. Nevada Street in the south to the entrance of Belltown's Battery Street Tunnel in the north, following previously existing railroad lines.

The viaduct was damaged in the 2001 Nisqually earthquake, and was proposed to be replaced, in part by a tunnel running beneath the city's downtown core.

The initial phase of demolition and removal of the viaduct began on October 21, 2011.

Earthquake concerns

The 1989 Loma Prieta earthquake destroyed the similarly designed Cypress Street Viaduct in Oakland, California with the loss of 42 lives. The 2001 Nisqually earthquake damaged the viaduct and its supporting Alaskan Way Seawall and required the Washington State Department of Transportation (WSDOT) to invest US$14.5 million in emergency repairs. Experts give a 1-in-20 chance that the viaduct could be shut down by an earthquake within the next decade. Since the Nisqually Earthquake occurred, semi-annual inspections have discovered continuing settlement damage.

Due to damage from continuing settlement, a group of researchers and faculty from the University of Washington urged the mayor of Seattle (in 2007) to close the viaduct within a four-year timeframe.

Planned replacement

Main article: Alaskan Way Viaduct replacement tunnel

On January 12, 2009, the state of Washington, King County, the city of Seattle, and the Port of Seattle revealed that they had agreed to replace the viaduct with a four-lane, 2-mile (3.2 km) long underground tunnel. The tunnel would have a south portal in SoDo, near CenturyLink Field, and a north portal near Thomas Street, north of the Battery Street Tunnel.

The project is estimated to cost US$4.25 billion, with the state, city, and county promising funding well short of the estimate. The state will fund boring of the tunnels, while the city and county will fund surface street improvements and repairs to the Alaskan Way Seawall, which itself was damaged in the Nisqually earthquake. Boring of the tunnel will begin in the summer of 2013 with the roadway scheduled to open in 2015.

The announcement did little to quell the long and heated debate over the viaduct's replacement, with several factions expressing their criticism over the tunnel decision.

Route description

Heading northbound on State Route 99, the viaduct begins about a mile (1600 m) north of the First Avenue South Bridge, passing over the west end of the Industrial District. Just south of Safeco Field, at Massachusetts Street, the bridge shifts from a side-by-side alignment to the double-deck alignment commonly associated with the Alaskan Way Viaduct, with northbound traffic on the upper deck and southbound traffic on the lower deck. Then, at approximately Pike Street, the bridge reverts to a side-by-side alignment for about ½ mile (800 m) until the viaduct's north end at the entrance to the Battery Street Tunnel.^{[citation needed]}

Entrances and exits

Mile	Entrances	Exits	Destinations
28.91	southbound	northbound	Spokane Street – West Seattle
28.91	northbound	southbound	West Seattle Bridge/Harbor Island
30.75	northbound	southbound	1st Avenue S./Safeco Field/Qwest Field/Colman Dock
31.30	southbound	northbound	Seneca Street/Downtown
31.95	northbound and southbound	northbound and southbound	Western Avenue/Belltown
32.44	northbound	southbound	Denny Way/South Lake Union

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  The view beneath the viaduct, facing south

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  Western Ave Exit to Belltown

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  The cutout of the Viaduct is just one of several unique features of the structure

See also

• Gardiner Expressway, an elevated freeway in Toronto with similar future plans.
• Embarcadero Freeway, a former elevated freeway along the waterfront in San Francisco that was demolished.
• John F. Fitzgerald Expressway, a former elevated freeway in Boston (Interstate 93) that was rerouted into a 3.5-mile (5.6 km) tunnel.

Bibliography

• Gilmore, Susan (September 8, 2006). "Two views of the viaduct" (article links to videos which require RealPlayer 10.5). Seattle Times. Retrieved 2006-09-10. 
• Gilmore, Susan (August 9, 2006). "State offers 3 decidedly different designs for viaduct". Seattle Times. Retrieved 2006-08-15. 
• Gilmore, Susan (2006-08-02). "Idea of fixing viaduct seen as having merit but problems as well". Seattle Times. Retrieved 2006-08-02. 
• Gilmore, Susan (July 25, 2006). "What will happen if viaduct closes? Study takes a look". Seattle Times. Retrieved 2006-07-25. 
• Lange, Larry (May 3, 2006). "A Longer shelf life for the viaduct". Seattle P.I. Retrieved 2006-06-24. 
• "Seattle's Little Dig". Seattle Weekly. April 19, 2006. Retrieved 2006-06-24. 
• "MorePerfect.org collected news stories". MorePerfect.org. 

External links

• SR 99 – Alaskan Way Viaduct & Seawall Replacement Project
• Alaskan Way Viaduct, Part 1: Early Transportation Planning
• Alaskan Way Viaduct, Part 2: Planning and Design
• Alaskan Way Viaduct and Battery Street Tunnel (Historic American Engineering Record)