Kiewit underway with $97M demo of Alaskan Way Viaduct, part of $3.3B replacement

Dive Brief:

Kiewit Infrastructure West Co. is underway with the demolition of the Alaskan Way Viaduct in Seattle, the final phase of the structure’s $3.3 billion replacement with the new State Route 99 tunnel. Removal of the viaduct will make way for the $712 million Waterfront Seattle Program.
In addition to demolishing the double-decked viaduct, Kiewit's contract includes the removal of two ramp structures; decommission, seal and fill the city’s Battery Street Tunnel; rebuild and raise to grade some streets and restore elements of the waterfront’s infrastructure to a temporary condition in preparation for the new waterfront.
The Washington State DOT (WSDOT) awarded Kiewit the contract in May 2018, but the contractor could not begin work until the SR 99 tunnel opened to drivers on Feb. 4.

Dive Insight:

The viaduct’s demolition marks the end of what has been, at times, a contentious and beleaguered construction process. The tunneling portion of the viaduct replacement project was delayed for about two years after the tunnel boring machine — dubbed Bertha —broke down in December 2013 and could not start tunneling operations again until December 2015.

Even after operations restarted, tunneling was halted about a month later by WSDOT and Washington Gov. Jay Inslee after a sinkhole appeared above Bertha’s path. Adding to the project’s problems, a barge carrying excavated soil — at about the same time as the sinkhole discovery was made — tipped over into the water close to where Bertha was tunneling, causing a potential hazard to workers and the public.

Work began once again after STP, a joint venture between Tutor Perini and Dragados USA, implemented a new soil monitoring and removal plan that temporarily halted some use of barges and trucked soil instead, before a new WSDOT barging plan was approved. In addition, a root analysis by STP maintained that the sinkhole may have been "a pre-existing void, a ground loss in the face of the [tunnel-boring machine], or a combination of both,” and tunneling was allowed to restart after STP filled the sinkhole with concrete.

With the viaduct’s replacement almost behind it, the city is now looking to the Waterfront Seattle Program. The initiative includes a $34 million expansion of the Seattle Aquarium; the Pike Place MarketFront ($34 million); the Alaskan Way and pedestrian promenade ($362 million); Pier 62 and Pier 63 rehabilitation ($100 million); and an overlook walk and east-west street improvements ($174 million). The Pike Place project is already complete, as is a new seawall. The city aims to reconnect the city to the waterfront through this group of projects, and has designed the program with sustainability and climate change in mind.