Shani Wallis, TunnelTalk
- An Hitachi Zosen EPBM is ordered by the Michels/Jay Dee/Coluccio JV for the first bored tunnel under the San Francisco Bay in northern California. The 4.56m diameter machine will excavate the 5-mile (8km) long water supply tunnel under the Bay as part of the $4.2 billion Water System Improvement Program for the San Francisco Public Utilities Commission. The alignment under the South Bay, south of the Dumbarton Bridge, will reach depths of 110ft (33m) as it progresses from a working shaft at Menlo Park on the Peninsula to another at Newark on the east side of the Bay.
Bay Tunnel alignment south of the Dunbarton bridge and of the trellised pipeline
- Project Manager for the JV Jim Stevens of Michels told TunnelTalk that the TBM order is to be signed shortly for delivery to the job site from the Hitachi factory in Sakai City, Osaka, Japan in about April next year (2011). "We are currently installing the 140ft deep diaphragm walls around the 58ft diameter working shaft ahead of excavating the core to about elevation -129ft," said Stevens. Once completed, the 12ft 10in (3.9m) i.d. segmentally lined tunnel will be fitted with a 108in (2.75m) diameter steel carrier pipeline backfilled into place. The segments of the primary lining are on order for supply from the Traylor Shea Precast plant in Stockton about 90 miles from the job site in Menlo Park.
- Tunnel designer Jacobs Associates specified EPB excavation for the drive through mostly stable clays. According to Stevens, the material is not described as abrasive in the GBR and only five or six inspection interventions into the excavation chamber are anticipated during the 5-mile drive. "The clay is also relatively impermeable and the machine is not expected to be subjected to the full hydrostatic head of the Bay." An outcrop of Franciscan bedrock near the east end of the tunnel will require the TBM be fitted with disk cutters for the final push to the reception shaft. Jacobs Associates designed the Bay Tunnel and Jacobs Engineering has the construction management contract.
- The Bay Tunnel TBM will be the second Hitachi Zosen TBM ordered by the JV partners. In Seattle, with Jay Dee in the lead, the Jay Dee/Coluccio/Michels JV has ordered a 21ft 2in (6.5m) o.d. diameter Hitachi EPBM to drive both 3,800ft (1.1km) running tunnels for Contract U230 of the Sound Transit University Link (U-Link) extension.
- The machine is also the fourth TBM order for Hitachi reported in recent times by TunnelTalk. In March 2010, the CEC-Soma JV ordered two new slurry TBM systems from the Japanese manufacturer for its 3.4km twin metro running tunnels contract in Bangalore, India. These are the first Hitachi Zosen TBMs and the first ever slurry TBM systems to be used in India.
SFPUB's Water System Improvement Program with the Bay Tunnel across the South Bay and location of the New Crystal Springs and New Irvington tunnels
- The Michels/Jay Dee/Coluccio JV won the Bay Tunnel contract by the slimmest of margins from three competitors in November last year (2009). Its bid of $215.3 million for the 5-mile (8km) long tunnel was only $97,000 below the second bid and almost $35 million below the Engineer’s estimate of $250 million. It is one of three major tunnelling contracts on the SFPUC's improvement program along with the 3.5-mile long, conventional roadheader excavation New Irvington Tunnel Project, awarded recently to the Southland/Tutor Perini JV, and the New Crystal Spring bypass tunnel on which the Shank/Balfour Beatty JV recently completed TBM excavation.
Fierce competition creates slimmest of margins for Bay Tunnel - TunnelTalk, Nov 2009
Bay Tunnel design (video) - TunnelTalk, March 2008
Water tunnels to recharge SFPUB's aging system - TunnelTalk, Sept 2009
Mobilization of Seattle's U-Link extension - TunnelTalk, July 2010
Underground advance for Bangalore Metro - TunnelTalk, Jul 2010
New Irvington Tunnel award - TunnelTalk, July 2010
Hole through for Crystal Springs drive - TunnelTalk, March 2010
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