State Route 99 tunnel

SR 99 tunnel
	A visualization of the tunnel
Overview
Location	Seattle, Washington, U.S.
Coordinates	47°36′37″N 122°20′41″W / 47.61028°N 122.34472°W
Status	Open
Route	SR 99
Start	South Dearborn Street; 47°35′48″N 122°20′09″W / 47.596534°N 122.335699°W
End	Harrison Street; 47°37′14″N 122°20′41″W / 47.620520°N 122.344674°W
Operation
Work begun	July 30, 2013
Constructed	2013–2017
Opened	February 4, 2019
Operator	Washington State Department of Transportation
Toll	$1.20 to $4.70
Technical
Length	9,270 feet (2,830 m; 1.756 mi)
No. of lanes	4
Operating speed	45 mph (72 km/h)
Tunnel clearance	15 ft 9 in (4.8 m)
Width	52 ft (16 m)
Route map

The State Route 99 tunnel, also known as the Alaskan Way Viaduct replacement tunnel, is a bored highway tunnel in the city of Seattle, Washington, United States. The 2-mile (3.2 km), double-decker tunnel carries a section of State Route 99 (SR 99) under Downtown Seattle from SoDo in the south to South Lake Union in the north.

Since the 2001 Nisqually earthquake, the replacement of the Alaskan Way Viaduct had been the source of much political controversy demonstrating the Seattle process. Options for replacing the viaduct, which carried 110,000 vehicles per day, included replacing it with a cut-and-cover tunnel or a bored 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.

Construction began in July 2013 using "Bertha", at the time the world's largest-diameter tunnel boring machine. After several delays, tunnel boring was completed in April 2017, and the tunnel opened to traffic on February 4, 2019.

^ Cite error: The named reference KN13 was invoked but never defined (see the help page).
^ "Tunneling toward a new SR 99; The SR 99 tunnel route (map)". Washington State Department of Transportation. Archived from the original on December 10, 2012. Retrieved December 8, 2012.
^ "Follow Bertha". Washington State Department of Transportation. Retrieved December 25, 2018.

[KN13-1] Cite error: The named reference KN13 was invoked but never defined (see the help page).

[tunneling-2] "Tunneling toward a new SR 99; The SR 99 tunnel route (map)". Washington State Department of Transportation. Archived from the original on December 10, 2012. Retrieved December 8, 2012.

[3] "Follow Bertha". Washington State Department of Transportation. Retrieved December 25, 2018.

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