As excavation of the recovery shaft for the Alaskan Way TBM repair in Seattle reached invert level, technical expertise to oversee the complex repair process has been appointed by the TBM’s manufacturer. TunnelTalk has learned that Gomez International of Arizona has been retained by Hitachi to assist in the process to remove, lift out, repair, lower and refit the cutterhead and main bearing drive unit of the 17.5m diameter EPBM.
Seattle Tunnel Partners (STP) confirms that disassembly of the SR99 tunneling machine is complete, and assessment of the damage is ongoing. The construction joint venture of Dragados and Tutor Perini will not provide a revised schedule to WSDOT for resuming mining until the scope of repairs is fully understood.
STP indicates it will replace the main bearing and outer seals of the machine, as expected. It has also decided to replace the inner seals to make them more compatible with the new outer seals and easier to access should the need arise. The new inner seals were designed and manufactured in Japan and are scheduled to arrive in late May.
Damage to the machine is more extensive in some areas than anticipated and some minor damage occurred during the disassembly process. For example, the outer seals and the steel retainers that hold them in place were destroyed. There was also damage to the cutter drive motor pinions and the main bearing bull gear.
As owner of the tunneling machine, STP and Hitachi are responsible for all aspects of the repair effort.
A senior engineer of the Gomez team of specialist mechanical, electrical and logistics engineers will assist to coordinate the activities of the subcontractors and crews engaged by Hitachi to complete its contractual commitment to repair the TBM to its designed and delivered working condition.
The Gomez International consultant has been on site in Seattle since December 2014 and will provide liaison between the subcontractors involved in the repair including crane operator Mammoet Company of The Netherlands which has installed one of the world’s largest tower cranes over the recovery shaft to lift and maneuver the world-record 17.5m diameter cutterhead and its main bearing drive unit; and specialists National Welding which will undertake up to as much as 150 tonne of welding required by the repair process. The repair process also includes a team of about 25 engineers from Hitachi assigned to Seattle, and the crews of engineers and laborers made available to the process by the project’s design-built contractor Seattle Tunnel Partners (STP), Dragados and Tutor Perini.
Gomez International knows well the TBM and its systems. It was engaged by Hitachi as its US machine and systems consultant during the procurement, design and manufacture of the mega machine and assisted Hitachi in preparing for strategic meetings with the Spanish/US client STP and the project owner WSDOT and their consultants and advisors. Its engagement with Hitachi was to proceed through the TBM assembly and commissioning stages but the company was released from its contract when STP took delivery of the machine at the port of Seattle.
As mechanical repair teams mobilize, WSDOT confirmed completion this week of the 24m diameter x 36m deep (80ft x 120ft deep) recovery shaft with installation of nearly 800m3 (1,000yd3) of rebar reinforced concrete to form the base slab and cradle on which the 17.5m (58ft) diameter EPBM will rest for its process of refurbishment and repair. Work will continue to prepare the seal and tunnel eye through which the TBM will emerge. Over the past 13 months since the TBM came to a stop in December 2013, maintenance crews have kept all its systems in operating order to ensure prompt start up and breakthrough into the recovery shaft. If the machine is unable to bore through the 6m (20ft) thick diaphragm wall of the shaft, a connection will be made from the tunnel eye in the shaft.
As well as its contract for the SR99 TBM repair in Seattle, Gomez is engaged as a consultant on several current tunneling projects in North America including two projects on which other Hitachi TBMs in the USA have been, and continue to be, used. Rick Gomez, as owner of the company, is committed on site also in Seattle on the Northgate Link of the extension of the Seattle Metro for the Jay Dee/Michels/Coluccio JV and was before that engaged by the same JV on its Capital Hill contract for the Seattle Metro U-Link project where a 6.5m EPB machine from Hitachi completed a total 1.1km of parallel running tunnels. The same machine has been refurbished and re-engaged on the Northgate contract along with a refurbished Robbins TBM. Earlier, in Seattle, Gomez was engaged by Obayashi to manage the logistics of completing the mechanical and electrical installations of its Beacon Hill tunnel and underground station contract for the Seattle Metro South Link project.
In California, Gomez International was engaged by the Michels/Jay Dee/Coluccio JV as mechanical subcontractor on the 4.56m Hitachi machine that recently completed a successful 8km-long water supply tunnel as the first ever bored tunnel under San Francisco Bay.
For about 25 years, the company has worked as a mechanical consultant for the US division of Japanese contractor Obayashi and was involved in its many hard rock TBM CSO tunnel drives in Atlanta; as well as the Eglinton Subway tunnel project in Toronto, Canada, and on construction by Obayashi of the high level Colorado River bridge to bypass the road that crosses on the crest of the iconic Hoover Dam.
A senior engineer with Gomez International, Asao Nomura, worked on the mega TBMs of more than 14m diameter used in the 1990s to excavate the Trans-Tokyo Bay highway tunnel in Japan, and who came to the United States more than 15 years ago to work for Obayashi on its first tunneling contract in North America for the CSO drainage program in Atlanta. Nomura, for Gomez International, was involved in its advisory role with Hitachi during the design, manufacture and procurement of the SR99 machine. Gomez and Nomura were interviewed by TunnelTalk during the visit to the Hitachi factory in Sakai, Japan for initial inspection and dedication of the machine by STP and WSDOT in December 2012.
For its part Hitachi has remained committed to the mega EPB machine in Seattle from the start of its operating troubles. Without knowing the root causes of the TBM breakdown - whether they be mechanical or operational - Hitachi has played a proactive role in recovering the situation. Since replacement of the main bearing was considered a prudent risk management strategy after failure of the main bearing seals, Hitachi has advanced its part of the process without delay. All replacement parts and components for the repair are on site and are being made ready for the process, and all the mechanical costs involved with repair of the TBM are being covered in this initial instance by Hitachi.
The mega 17.5m (58ft) EPB machine procured by STP for its US$1.35 billion design-build SR99 Alaskan Way viaduct highway replacement tunnel contract in Seattle is the largest TBM in the world so far, and the first soft ground TBM of more than 9m (30ft) diameter to operate in the USA. As well as the three Hitachi machines in America (for the Seattle SR99 highway, the Seattle Sound Transit Metro contract, and the San Francisco Bay water tunnel), Hitachi has two slurry TBMs working currently in Bangalore, India, on its metro construction; a further six working on metro contracts in Singapore; and several more working on tunnel contracts in China. Hitachi was also one of the manufacturers involved in the design, manufacture and supply of the eight mega machines of more than 14m diameter used on the Trans-Tokyo Bay highway tunnel in the 1990s.
The SR99 TBM is not the first machine in the world to experience serious problems and it will not be the last. All similar incidents in the past have been repaired, recovered and restarted to complete the project successfully. The same is possible and planned for the mega machine on the SR99 project in Seattle.