Bertha breakup after breakthrough 21 Sep 2017

After its record-breaking breakthrough in April in Seattle, workers have worked six days/week, 20 hours/day to dismantle TBM Bertha and remove all trace of the 17.48m diameter machine, leaving in its wake a segmentally lined tunnel of impressive scale and quality.

Workers begin breakup and removal of Bertha

As the torches began their work to cut up the massive components of the world’s largest ever TBM when it launched in 2013, parts of the machine were being donated by machine manufacturer and owner Hitachi Zosen as historical artifacts of the tunnel achievement to different organisations in the city.

The Seattle Times newspaper, which has followed the progress of Bertha and of the project day by day from the beginning, reports that the city’s Museum of History & Industry (MOHAI) has taken delivery of two control-room consoles and four cutting tools from the TBM. The Museum is a popular destination in Seattle and particularly for children who enjoy the exhibits and displays of major industrial achievement. The consoles are preserved as the control centres of the giant TBM and all its mechanical operations that excavated the double deck four lane tunnel which will ultimately allow the dismantling of the double deck Alaskan Way elevated highway that has dominated the waterfront of the city since it was built in the early 1950s.

In addition, the Port of Seattle has salvaged large pieces of giant cutterhead including the triangular center piece. These heavy steel pieces, too heavy for display in the Museum, are planned one day to be monuments to the project and installations of urban sculpture along the waterfront once the elevated viaduct is taken down and disappears.

Many other parts of the machine and its trailing backup are retained by Hitachi Zosen for refurbishment and recycling while all else is cut up for scrap metal by a company in Seattle.

As the TBM was being dismantled, thousands of meters of conveyor belt was also being dismantled. All muck from the EPB TBM was transferred by a continuous conveyor system from the machine through the tunnel and up and over the port to barges at the loading zone for onward disposal.

As remnants of the tunnel excavation process are removed from site, work continues by the Seattle Tunnel Partners construction joint venture of Dradagos and Tutor Perini to complete the highway tunnel project. As the TBM advanced, the upper deck of the double deck highway was cast in place and is now more than 75% complete according to project owner WSDOT, the Washington State Department of Transportation. The lower northbound deck is being formed of precast concrete panels, installation of which begins once all the trailing gantries, services and pipelines and walkways behind TBM Bertha are removed from the tunnel.

Thousands of meters of continuous conveyor system in rewind

Predictions are that the roadway decks should be complete by end of this year (2017) and the tunnel ready for traffic by early 2019. In addition to the tunnel, major works are in progress to link the tunnel to the existing SR99 highway at each end and a programme for removal of the Alaskan Way viaduct, which is also part of the STP contract, is being prepared.

The 2km long tunnel, at $2.1 billion, is the largest part of the $3.2 billion project by WSDOT for replacement for the aging and earthquake damaged Alaskan Way Viaduct. It is reported that another $480 million in costs overruns associated principally with technical breakdown and costly repair over two years of the TBM, is in dispute among the major stakeholders - STP, WSDOT, the insurers and Hitachi Zosen.

In a statement issued in April, WSDOT stated the following as the facts:

Cost overruns:
WSDOT asked the legislature for $60 million dollars for the next budget (2017-19) to pay for added program costs from the tunnel project delays. Last year it told the legislature that costs could go as high as $149 million due to risks in tunneling. Tunneling is now complete and that $149 million estimate may decrease.

Crew poses proudly with Bertha after operating it to successful breakthrough

The pipe:
It is the contractor’s claim that a hollow, 8in steel well casing caused the damage to the tunneling machine. WSDOT disagrees with the contractor’s assertion that the pipe caused the damage. The contractor paid for the repairs and has requested reimbursement. What caused the damage is a matter of litigation.

Project delay:
The tunnel was originally scheduled to open in December 2015. It is now estimated to open in early 2019, three years later.

The cost of the tunnel:
The tunnel contract is $1.4 billion. The adjoining road projects bring the total tunnel costs to $2 billion. It is not accurate to say the tunnel cost $3.1 billion as that is the cost of the entire program to replace the viaduct which comprises 32 different projects including viaduct demolition and decommissioning of the short Battery Street Tunnel which is on the SR99 Alaskan Way route that will be bypassed by the new tunnel.

Reporting now moves from a tunnel excavation project to completion of the new highway tunnel infrastructure and settlement of the claims for cost overruns and delays.