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Seattle set to open underground highway 31 Jan 2019

Shani Wallis, TunnelTalk

The Seattle foreshore and the city’s traffic flow is set to be transformed from this weekend, 2 and 3 February, when traffic on the elevated Alaskan Way viaduct will be redirected through its replacement double-deck highway tunnel under the heart of the city. After seven years in construction, the supersized 17.4m o.d. TBM bored tunnel is now ready to open in grand celebration ceremonies across the weekend and make way for demolition of the ageing, earthquake-damaged structure that has blighted the seafront for more than 60 years. As part of the project, the Battery Street Tunnel on the route to the viaduct will also close forever and be backfilled to avoid any further access.

TunnelTalk has followed development and progress of the viaduct replacement tunnel since its earliest days of feasibility and has tracked all the challenges and triumphs of the project. The grand opening festivities of the weekend will comprise a fun-run, a bike-ride sponsored by leading tunnel engineering consultant HNTB, and a walk-through of the 2-mile (3.2km) long tunnel. Thousands of Seattle residents and visitors have registered to be part of the public celebrations, which will include tunnel and viaduct tours, a Battery Street Tunnel walk-though, and a festival on the elevated viaduct before it disappears. Politicians and project leaders will be on hand for a ribbon cutting ceremony to open the tunnel for a first official drive through of the new infrastructure. An interactive Lego model of a TBM and a life-size mural of the TBM Bertha's cutterhead will link the public to the mammoth TBM excavation undertaking at the heart of the new infrastructure.

The viaduct has been closed to traffic for the past three weeks as the realignment ramps and connections to the replacement tunnel were completed and readied for the start of its public service on Monday 3 February. Demolition of the viaduct will begin after the tunnel opens and continue until end 2019/early 2020.

Demolition of the elevated Alaskan Way viaduct (left) and rerouting of the traffic through the replacement tunnel will transform the waterfront of Seattle (right)
Demolition of the elevated Alaskan Way viaduct (left) and rerouting of the traffic through the replacement tunnel will transform the waterfront of Seattle (right)

“By opening the tunnel and removing the viaduct, we are setting the stage for a historic transformation in our State’s largest city and throughout the region,” said Washington State Governor Jay Inslee. “The end of the viaduct marks the beginning of an exciting new era in our State’s transportation history.”

TBM bored tunnel replaces the viaduct and the Battery Street Tunnel
TBM bored tunnel replaces the viaduct and the Battery Street Tunnel

Leading up to the grand opening weekend and through 2018, the SR99 tunnel contractor, STP - Seattle Tunnel Partners - completed the tunnel roadway and installed and tested thousands of components that together make up the tunnel operating systems. STP reached substantial completion of its contract in October and turned over control and ownership of the tunnel to the project owner, WSDOT, the Washington State Department of Transportation.

During this time, WSDOT continued systems testing and training of tunnel operations and emergency response staff.

While STP worked on the tunnel, other contractors began their work. At both tunnel portals, the SR99 connections project contractor Scarsella Brothers, began working on the eight ramps connecting the tunnel to local streets. In May 2018, Kiewit Infrastructure West was awarded with the contract to remove the viaduct, close and seal the Battery Street Tunnel, and rebuild surface streets near the tunnel north portal. A total of $156 million in extra funds have been requested by WSDOT of the taxpayers to complete these final works. WSDOT said in a statement that none of these additional funds will be used to pay for tunneling machine repairs, adding that WSDOT continues to follow insurance claims and litigation of the tunnel project’s design-build contract to recover added expenses incurred by the tunneling delay.

TunnelTalk reporting of the replacement tunnel project - its development, the construction contract and the TBM selected to complete the excavation, the breakdown and repair of the TBM, the relaunch of the repaired machine, the steady progress to final breakthrough in April 2018, and the strained relationships between the parties to the project - is all chronicled in the TunnelTalk references below.

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