This $12.7-billion project is a six-mile, four-station extension of the BART system.
After years of technical analysis, public input and federal review, the Santa Clara Valley Transportation Authority (VTA) recently selected the single-bore tunnel as the preferred design method for the five mile-long tunnel portion of BART Silicon Valley Phase II (BSVII). This $12.7-billion project is a six-mile, four-station extension of the regional BART system from downtown San Jose to the City of Santa Clara.
The VTA Board of Directors said the single-bore method avoids the high cost, complexity and downtown disruption associated with an alternative concurrent tunneling approach of using two boring machines—an alternative that would have required cut-and-cover excavation in the heart of San Jose.
VTA says going with a single bore—which is estimated to cost around $3 billion—is the “most viable option, offering the best balance of constructability, feasibility and lower overall risk.” This decision allows VTA to advance project design towards 60%, stay on a critical path to tunnel construction and meet the projected revenue service date, say officials.
Before work can begin, VTA will go through a competitive procurement process to bring on a new tunneling contractor. As of now there is no short list of contractors, says VTA spokesperson Stacey Hendler Ross. “After an initial round of industry outreach conducted at major tunnel conferences earlier this year, VTA met with ten heavy civil construction and tunnel contractors to discuss delivery methods, contract packaging size, scope and other contractual areas,” she says.
VTA says it anticipates releasing the Request for Proposals for the new tunneling contract in the first quarter of 2026 with a contract award anticipated in the second quarter of 2027, and tunneling construction eventually starting in 2029.
A joint venture of Kiewit Infrastructure West, JF Shea Construction and Traylor Brothers (KST) was originally selected in 2022 to lead tunnel construction, but after receiving repeated proposals exceeding twice the project budget, VTA last June decided to look for another tunnel contractor.
“Based on initial industry feedback received from earlier this year and work done to date, VTA plans on issuing a new tunnel procurement to increase bid competitiveness, which includes review of contractual terms, risk sharing opportunities and contract size,” said Ross. “Additional details of what we will be requesting will be included in the request for proposals. We will additionally be conducting additional industry outreach throughout the coming year.”
Kiewit Shea Traylor Joint Venture is still on the project, constructing early construction activities including the tunnel boring machine launch structure.
Looking ahead, one of the largest challenges with constructing a tunnel in the South Bay is the challenging ground conditions and high water table, says Sarah Wilson, BART Silicon Valley Phase II Construction Director.
“We will be essentially operating a train system in five stories of space underground and at the same time keeping the excavation safe in challenging ground and groundwater conditions,” says Wilson. “Keeping this operation moving smoothly and safely requires expertise and management of the highest caliber.”
Much of the current work on the BSVII project is taking place at the Newhall Yard and West Portal site, located on the border of San Jose and Santa Clara, just west of the San Jose airport. Crews are currently constructing the tunnel boring machine (TBM) launch structure—a massive excavation that reaches over 130 ft deep at one end and rises to the surface. This will be the starting point for the TBM’s journey once it arrives from Germany, and later, the location where trains will enter and exit the tunnel.
To prepare the tunnel site, crews are installing reinforced underground support walls built from huge rebar cages, some weighing up to 150 tons. Excavation of the launch structure is also underway, with hundreds of truckloads of soil being hauled daily as crews shape the tunnel’s future gateway.
Besides KST completing early construction activities, there are several teams working on BART Silicon Valley Phase II. The program management team is a joint venture of HNTB and WSP, the general engineering consultant is a joint venture of Mott MacDonald and PGH Wong, and the construction management services are being provided by Bechtel. Ross says there will be several more contracts that come out to construct the rest of the BSVII Project in the coming years.
The BSVII Project is Santa Clara County’s largest public infrastructure project. With four stations, the project will serve 55,000 weekday riders when complete.
