Paula Wallis, TunnelTalk

Fig 1. Warm Springs extension

Construction is set to begin on a critical link in the 16.3 mile extension of BART into Silicon Valley. BART (Bay Area Rapid Transit) will hold a groundbreaking ceremony next Wednesday (September 30, 2009) for the Warm Springs Extension that includes a short cut-and-cover section and will extend BART 5.4 miles south to the Santa Clara County boarder (Fig 1).

Last month (August 24, 2009) BART issued a notice to proceed to the Shimmick/Skanska JV to begin the project's underground phase that is expected to last for three and a half years.

The JV was awarded the $136 million first phase contract that includes the construction of a cut-and-cover subway from just north of Stevenson Boulevard, under Fremont Central Park, including a portion of Lake Elizabeth, and beneath the Union Pacific Railway freight track to just north of Paseo Padre Parkway. The contract also includes construction of two ventilation structures and relocation of a number of amenities within Fremont Central Park, including the Dog Park, Basketball Courts, and related parking.

Later this year, BART plans to seek bids for the second phase of the Warm Springs Extension, which includes above-ground elements, including the line, trackwork, and construction of the Warm Springs Station. Construction is slated to begin in 2010 and conclude in 2014.

Shimmick Construction is a general engineering contractor based in Oakland, California, and founded by John C. Shimmick. The company has been responsible for more than $2 billion of work since its inception in 1990. It has partnered in joint ventures with Obayashi and Balfour Beatty Rail Inc. in the past, never for a tunneling project. This is its first joint venture with Skanska. Headquartered in Stockholm, Sweden, Skanska is one of the 10 largest construction companies in the world with more than 60,000 employees.

As constructions on the Warm Springs extension gets underway, the BART to Silicon Valley extension is moving forward.

Fig 2. Silicon Valley extension

The Warms Springs extension terminates at the Alameda, Santa Clara County boarder, where the Santa Clara Valley Transportation Authority (VTA) takes responsiblity for delivering a 16.3 mile extension to Milpitas, San Jose and Santa Clara.

The preferred alternative includes, a 5-mile tunnel under downtown San Jose with six stations, one in Milpitas, four under San Jose and one in Santa Clara. The extension will also include a new maintenance and storage facility in Santa Clara (Fig 2).

VTA is pursuing Federal environmental clearance on the extension, said Bernice Alaniz, VTA spokesperson. "We submitted the EIS (Environmental Impact Study) in August and are expecting comments back from the Federal Transportation Administration this Friday (September 26, 2009). We anticipate a Record of Decision (ROD) from the FTA (Federal Transit Administration) and approval of the final EIS by February 2010. A ROD qualifies the VTA to receive Federal funding, enter into final design and begin pre-construction activities."

Alaniz said that VTA also submitted an application this month requesting $850 million in New Starts Program funding and is anticipating a decision in early 2010. A positive decision will allow construction to begin on the first 10 miles of the BART Silicon Valley Extension.

The total project cost is estimated at about $6.13 billion in 2008 dollars. A half cent sales tax increase and other local sources would contribute 77% of the funding for the project. The State of California's Traffic Congestion Relief Program (TCRP) would contribute 11% and Federal grants, including the New Starts Program, would provide the remaining 12% (Fig 3).

Fig 3. Funding sources

In July 2009 VTA was allocated $40 million in TCRP funds by the California Transportation Commission (CTC). This is the first of an anticipated six installments that will total almost $240 million. The $40 million allocation is designated for project engineering during the final design stage.

The San Jose underground section comprises twin bore tunnels about 22,780ft long x 18ft diameter and will run 10ft to 75ft below the surface. Center-to-center tunnel bore spacing would be about 40ft, providing a pillar width between the tunnels of about one tunnel diameter.

Under this alternative the VTA will procure two EPB TBMs to excavate the tunnels. Procurement would include the design and manufacture of the machines, factory assembly and testing, delivery to site, assistance with assembly onsite, support throughout tunnel construction, and supply of spare parts. The process of procurement would begin with pre-qualifying manufacturers who can then bid on the contract.

Confirmation of the Record of Decision and allocation of Federal funding will determine the construction schedule.

References

A slow road for BART to San Jose - TunnelTalk, May 2007
Silicon Valley selects BART line consultants - TunnelTalk, Dec 2003