The central waterfront section of the SR 99 Alaskan Way Viaduct will be replaced with a bored tunnel beneath downtown Seattle. The tunnel will connect to the new SR 99 roadway south of downtown, and to Aurora Avenue in the north. The Federal Highway Administration (FHWA), WSDOT and the City of Seattle released the project's Final Environmental Impact Statement in July 2011, and FHWA signed the Record of Decision in August 2011.
Seattle Tunnel Partners is the design-build contractor for the SR 99 tunnel. Design-build combines project design and construction in a single contract. Key members of Seattle Tunnel Partners, a joint venture of Dragados USA and Tutor Perini Corp., delivered the comparable 49.5-foot-diameter Madrid M-30 highway tunnel in Spain. The team includes local firms Frank Coluccio Construction, Mowat Construction and HNTB Corp. Hitachi Zosen Corp. is designing and building the tunnel boring machine.
This project is part of the Alaskan Way Viaduct Replacement Program.
Why is WSDOT
replacing the SR 99 Alaskan Way Viaduct?
The Alaskan Way Viaduct plays a major role in sustaining our economy and maintaining our citizens' ability to travel to and through Seattle. However, the viaduct is at risk of failure from earthquakes, with unacceptable risk to lives as well as property. The structure must be replaced.
The End Result
The SR 99 tunnel will move the state highway underground, reconnect the street grid at the ends of the tunnel and remove the viaduct along Seattle’s downtown waterfront. It will maintain a vital route for people and goods through downtown, while opening up more than nine acres of public space for a world-class waterfront.
- Drive-through simulation (YouTube or Windows Media Player) shows an early design concept for the tunnel and the access provided at its north and south portals.
- Underground simulation (YouTube or Windows Media Player) shows the tunnel’s route beneath downtown Seattle and its proximity to other underground structures.
Project Benefits
- Improves safety: The tunnel will be a safe, seismically sound replacement for the Alaskan Way Viaduct. It is being designed to withstand major earthquakes and to include state-of-the art safety features.
- Maintains mobility: The viaduct section of SR 99 is a main north-south route through Seattle. Many commuters and industries, particularly the Port of Seattle, depend on this corridor as an alternative to I-5. Replacing the viaduct with a tunnel ensures this capacity is available as the region grows.
- Minimizes disruption: Boring the tunnel allows us to keep SR 99 open during construction, maintaining a route for people and goods through downtown.
What is the project timeline?
January 2009: Governor, King County Executive, Seattle Mayor and Port of Seattle CEO recommend replacing the viaduct's central waterfront section with a bored tunnel beneath downtown Seattle, a new waterfront surface street, transit investments, and city street and waterfront improvements.
April 2009: Legislature endorses bored tunnel.
October 2010: Release Supplemental Draft Environmental Impact Statement that analyzes bored tunnel alternative.
January 2011: Sign contract with Seattle Tunnel Partners for design and construction of the SR 99 tunnel. Preliminary design continues.
July 2011: Release project’s Final Environmental Impact Statement.
August 2011: FHWA signs Record of Decision. WSDOT issues notice to proceed to Seattle Tunnel Partners for final design and construction.
Late 2011: Begin manufacturing of tunnel boring machine.
Early 2012: Begin boring machine launch pit construction south of downtown Seattle.
Mid 2013: Begin tunnel boring.
Late 2014: Complete tunnel boring.
Late 2015: Open SR 99 tunnel to traffic.
Financial Information
Project budget: $2 billion
This amount includes design, right of way, construction management, risk and inflation. The project has committed funding from the state gas tax and local and federal sources. The 2009 Legislature stated the finance plan must include no more than $400 million in toll funding.
Design-build contract total: $1.35 billion
Most of the tunnel work will be done as part of a contract that combines project design and construction. This contract, awarded to Seattle Tunnel Partners, includes tunnel boring, mitigation for tunnel settlement, construction of tunnel portals, building the road within the tunnel and constructing two operations buildings. More than 90 percent of the design-build work will be performed for a fixed price.
How can I get more information?
Contact:
Chad Schuster
Communications
Phone: 206-805-2869
E-mail: SchustC@consultant.wsdot.wa.gov
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