Proposed replacement of the Alaskan Way Viaduct
A visualization of the future tunnel
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| Overview | |
|---|---|
| Location | Seattle, Washington, U.S. |
| Coordinates | 47°36′37″N 122°20′41″W / 47.61028°N 122.34472°WCoordinates: 47°36′37″N 122°20′41″W / 47.61028°N 122.34472°W |
| Status | Under construction |
| Route |
 SR 99
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| Start | 47°35′48″N 122°20′09″W / 47.596534°N 122.335699°W |
| End | 47°37′14″N 122°20′41″W / 47.620520°N 122.344674°W |
| Operation | |
| Work begun | July 30, 2013 |
| Operator | Washington State Department of Transportation |
| Traffic | Automotive |
| Technical | |
| Length | 2 miles (3.2 km) |
| No. of lanes | 4 |
| Route map | |
![Map of tunnel route[2]](https://en.wikipedia.org/wiki/File:Route_map_of_Alaskan_Way_Viaduct_replacement_tunnel.png) |
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The Alaskan Way Viaduct replacement tunnel is a bored road tunnel that is under construction in the city of Seattle in the U.S. state of Washington. The 2-mile (3.2 km) tunnel will carry State Route 99 under Downtown Seattle from the SoDo neighborhood to South Lake Union in the north.
Since 2001, the replacement of the Alaskan Way Viaduct has been the source of much political consternation demonstrating the Seattle process. Options for replacing the viaduct, which carries 110,000 vehicles per day, included either replacing it with a cut-and-cover tunnel, replacing it with another elevated highway, or eliminating it while modifying other surface streets and public transportation. The current plan emerged in 2009 when government officials agreed to a deep-bore tunnel.
Boring of the tunnel with the world's largest-diameter tunnel-boring machine (TBM) "Bertha" began on July 30, 2013.
The project, which was originally scheduled for completion in December 2015, was halted on December 6, 2013 after an unknown stoppage approximately 1,083 feet (330 m) into the planned 9,270-foot-long (2,830 m) route. Investigations a month later revealed that the machine had damaged several of its cutting blades after encountering a steel pipe that was used to measure groundwater in 2002 around the Alaskan Way Viaduct. Over the next two years, a recovery pit was dug from the surface in order to access and lift the machine's cutterhead for repair and partial replacement. Bertha resumed tunnel boring on December 22, 2015. As of July 2016[update], WSDOT estimated that the tunnel would be completed and open to traffic in early 2019. On January 18, 2016, Governor Inslee stopped tunneling due to a sinkhole above Bertha near the launch pit. Tunneling resumed on February 23, 2016 and broke through to the exit pit on April 4, 2017.
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Wikipedia