Design and Construction
The approved design is a four-lane, 2-mile (3.2 km) long bored underground tunnel. The tunnel will have a south portal in SoDo, near CenturyLink Field, and a north portal in South Lake Union, east of Seattle Center. The route goes beneath Pioneer Square, the central business district of Downtown, and Belltown.
The project is estimated to cost US$4.25 billion, with $2.8 billion coming from the state and federal governments to cover the tunnel boring and a new interchange in SoDo. The replacement project also includes the following projects and funding sources:
- The city of Seattle will fund surface street improvements, utility relocation, and repairs to the Alaskan Way Seawall, which was also damaged in the 2001 Nisqually earthquake.
- Since the proposed tunnel will contain two lanes in each direction as opposed to the viaduct's three, and no Western Avenue exit to serve the Belltown, Interbay, Magnolia,and Ballard areas, King County will fund transit improvements to offset the loss.
- The Port of Seattle is considering funding part of the project in SoDo.
- $200 million will be collected from tolls.
WSDOT began part of the larger project in 2008, while the replacement debate was still on-going, by repairing some of the viaduct columns. Tunneling is scheduled to begin in 2013 and the tunnel itself is scheduled to open to the public in 2015.
The $80 million tunnel boring machine (TBM) was created for this project by Hitachi Zosen Corporation near Osaka, Japan. The 326 ft (99 m), 6,700-short-ton (6,100 t) TBM was disassembled into 40 pieces and shipped to Seattle where it will be reassembled in the launch pit near the south end of the future tunnel. From there, the record-breaking 57.5-foot (17.5 m) diameter borer will gradually proceed in 6.5 ft (2.0 m) increments toward the north end.
WSDOT nicknamed the TBM "Bertha" after Seattle's first female mayor, Bertha Knight Landes. This name was chosen from names submitted by kindergarten through 12th grade students for a naming competition.
The initial phase of demolition and removal of the viaduct began on October 21, 2011. Only a southern portion of the viaduct was removed at that time; the viaduct along the central waterfront will remain open for traffic until the tunnel is complete.
Read more about this topic: Proposed Replacement Of The Alaskan Way Viaduct
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