Paula Connor TunnelTalk

When plans to bring BART to San Jose were first floated in the 1960s, the price tag was in the hundred millions. Today it has ballooned to $4.7 billion and every year of delay adds another quarter of a billion in inflation to the price. So there is a real sense of urgency to push the project forward. TunnelTalk reports on the current state of play.

The 16.3 mile (26.2km) extension of the Bay Area Rapid Transit (BARl) from Fremont down the East Bay to the South Bay includes six stations, three of them below grade, and a 5-mile (8.2km) subway under San Jose (Fig1).

"This extension is absolutely necessary to the Silicon Valley and to regional transportation solutions", said Rod Diridon, Executive Director of the Mineta Transportation Institute in San Jose, and board member of the California High Speed Rail Authority. "The public wants BART and the longer we delay the more it's going to cost. Voters approved a 30-year half-cent sales tax levy in favor of the extension and other transportation projects in 2000."

Extension alignment to San Jose

Those same voters however then rejected a half-cent sales tax for transportation projects in June 2006 and will likely be asked to pass a quarter to half-cent sales tax levy again in 2008 to raise the $75 million a year promoters say is needed to pay for day-to-day operations.

But while the project remains in financial limbo, an injection of State funds is keeping hope alive. In February 2007, The California Transportation Commission released $364 million for the project - $151 million to reimburse the Santa Clara Valley Transportation Authority (VTA) for preliminary design and another $213 million for further design work.

Before release of the State funds, the VTA made a critical decision to spend $185 million to purchase track rights from Union Pacific and continue preliminary engineering for a further two years.

From Fremont on the Oakland side of San Francisco Bay, the extension runs at grade to a cut-and-cover portal and into 4.3 miles (6.9km) of twin 18ft (5.4m) diameter running tunnels, at up to 75ft (23m) below the surface, at about 40ft (12m) center-to-centre, and through three open-cut stations - Alum Rock, Downtown San Jose and Diridon/ Arena.

Geotechnical investigations conducted by EarthTech of Long Beach, California, show soil conditions generally consist of low to medium plasticity/stiff clays with interbeded clayey sand, silty sand and gravel layers with a water table located at 5-15ft (1.5-4.6m) below the surface. Studies of 76 geotechnical borings and 146 cone penetrometer tests were conducted along the alignment, with sampling depths ranging up to 220ft (67m) deep.

Two EPBMs will be used to excavate lightly over-consolidated alluvial soils beneath the water table, and build single-pass bolted and gasketed pre-cast segmentally lined tunnels. Open cut will be used for the mid-tunnel vent shafts and a downtown crossover.

In an attempt to accelerate the schedule, the VTA has departed from conventional contracting practices and will procure two 6.2m diameter TBMs itself. Procurement would include design and manufacture of the machines, factory assembly and testing, delivery to the site, and support and spare parts supply throughout the construction.

The Hatch Mott MacDonald and Bechtel, retained by the VTA to design and manage construction,the tunnel, recommended the OPP and is championing the VTA's decision in this particular case.

"OPP is not for every owner or project," said John Hawley, Project Manger for Hatch Mott MacDonald (HMM), "but in high density urban settings, with difficult ground conditions, demanding alignment and tight schedules, it's a good fit."

A paper at the RETC 2005 titled 'Owner procured tunnel boring machines' and co-authored by HMM engineers (detailed the rational for the controversial practice as a way to manage risk and accelerate project timelines.

"The TBM poses a significant risk", said Hawley. "It can impose terrific cost and schedule impacts on a project if it's not suitable for conditions. And the TBM is usually ordered when the notice to proceed is granted, which means it could take up to 12 months for it to arrive on site. If the owner procures the machines they can be ready go when notice is given."

Hawley also said the owner and its consultant have a greater understanding of the ground conditions, having spent a great deal of time investigating them, yet contractors in the traditional bidding process, who have little time to review the geotechnical information, make critical decisions on the features of the TBM. Further, TBM selection and features can also be compromised by the competitive bidding between the contractor and TBM manufacturers.

"OPP means the choice of the TBM is taken out of the low bid environment and the owner and its consultant, who have greater understanding of the project, specify the best TBM for the job", said Hawley.

But contractors are reluctant to give up control. Many argue the practice will reduce the number of bids. An engineer with a major contractor told T& TNA that his company decided not to bid a project because it was an OPP. He said they would have been forced to operate a machine that may not have been right for the project, and while the owner may take on the risk, the contractor still has to deliver the job.

Another engineer with experience of OPP and who also wanted to remain anonymous agreed. He felt the owner supplied an inferior machine for the project he worked on and argued that contractors who have worked with a TBM supplier over years and had built up a trust - that preferred relationship is lost in the OPP.

The practice was first introduced in 1970 in Melbourne, Australia and has been used in a least 10 projects since including the St Clair River Rail Tunnel between Ontario and Michigan in 1992; the London Water Ring Main in 1991; and most recently Singapore's Changhi Metro Line in 2000.

The TBM requirements under a OPP are usually determined during preliminary design with selection of the manufacturer and procurement of the tunnel lining confirmed during final design. Pre-qualified contractors are included in the process, ahead of the TBM and lining being selected.

The VTA must clear several hurdles however before becoming the first in California to adopt OPP. The greatest hurdle will be securing the funding. To date, the Authority has received a total $409 million from the state and is looking for another $650 million from California's Transportation Congestion Relief Program to match a full funding grant agreement of $750 million in FTA federal funding.

In 2004 federal officials gave the project a 'not recommended' rating due to the region's 'dot-com' recession. In December 2005 the VTA asked the FTA to temporarily withdraw the project from the new starts process.

The decision was made to reevaluate the project's cost, ridership estimates and it's financial plan. A move designed to improve the project's ability to compete for federal funding began in early 2007 and will continue through 2010.

If funding is secured, construction could start in 2008 for services to open in 2016.