California Construction News staff writer
The Santa Clara Valley Transportation Authority and BART say construction on the downtown San Jose extension will start by 2024.
Design and construction officials with BART and the VTA held a joint meeting Aug. 26, announcing that tunnel boring and other heavy station construction activities are likely to start in within the next two years, “barring unforeseen delays”.
the first in a series of construction contracts for the BART Silicon Valley Phase II (BSVII) project – for tunnel and trackwork is a $235 million progressive design build contract that was awarded in May to Kiewit Shea Traylor (KST).
More in-depth information on the plan and station refinements will be shared at the VTA Board workshop Sept. 16.
As part of the design process, the tunnel and trackwork contractor, Kiewit Shea Traylor (KST,) is exploring and analyzing dozens of changes that could result in more efficient delivery and ultimately enhance the project. These ideas take into consideration the cost and construction timeline, as well as safety, operations and maintenance, and passenger experience.
One of the key proposed ideas includes a center boarding platform within the single bore tunnel (meaning, a platform between both directions of tracks) for all three underground stations – 28th Street/Little Portugal, Downtown San Jose, and Diridon Station.
This design idea would allow for:
- side by side tracks for the entire 6-mile extension
- a shallower descent to the platform from the street level
- potential access to the boarding platforms from both sides of Santa Clara Street, in Downtown San Jose
VTA and its contractor are using a delivery approach to the project that allows for more engagement and ongoing collaboration with key stakeholders and the community as the design advances before construction begins. During this “design innovation” period, VTA is working with a task force of public and private transportation professionals to identify potential station refinements.
Efforts will enhance access to stations, promote Transit-Oriented Development, and spur economic growth.
The six-mile extension will add stations in four new locations – 28th Street in San Jose’s Little Portugal, Santa Clara and Market streets in downtown San Jose, the San Jose Diridon rail depot and near PayPal Park in Santa Clara.
As a result, it is expected that more than four miles of rail tunnel under downtown San Jose along Santa Clara Street.
Officials say the process will include boring under the city instead of “cut and cover” methods to build the tunnel.
“What we deeply care about is building the best project, the most equitable project ever that connects the Bay Area and our communities together in a way that we would have never believed possible,” said BART Board Director Janice Li.
Under previous design proposals, the subterranean BART stations would be encased in a single tunnel bore, with the platforms for north and southbound trains stacked on top of each other.
However, officials said last Friday that the proposed subterranean station designs will now feature a single platform sandwiched between parallel tracks for trains traveling in either direction, a design similar to BART stations like that of Embarcadero station in San Francisco.
The modification — suggested by the project’s design build contractor Kiewit Shea Traylor Joint Venture, or KST — would widen the proposed tunnel bore by roughly five feet and is expected to be easier to maintain, cheaper to construct and more efficient to access both for riders and emergency responders.
The single platform is also expected to improve ventilation for the tunnel, according to Takis Salpeas, the project director for the San Jose extension, because it will include a 13-foot-by-17-foot cavity under the tracks.