Activity at the Newhall Yard, home of the future Santa Clara BART station, has increased in the past few weeks. Crews are preparing the yard for the arrival of the Tunnel Boring Machine. The machine will create a five-mile long underground tunnel that will connect Santa Clara to Diridon Station in San Jose.
According to the Valley Transportation Agency (VTA), the early construction activities will take about two years to complete. This includes bringing and assembling the Tunnel Boring Machine, creating an on-site factory to create tunnel lining segments to be inserted during the boring and a grout plant for use during tunnel construction.
As excavation begins, the Newhall Yard will become the site for storing and hauling soil from the tunnel.
To minimize impact to the outside world, VTA will use noise curtains and clean the trucks before they leave the construction site. There are no expected detours or lane closures around the site during this preparation phase. Much of the construction traffic will be confined to going to and from I-880 from Coleman Avenue.
The entire length of the connector will span about six miles, with five of those miles traveling approximately 90 feet underground. The tunnel itself will be approximately 50 feet in diameter, which is equivalent to the length of a semi-truck with trailer.
The VTA says that the tunnel will be beneficial on many levels.
“Constructing this tunnel via a single-bore approach allows for much of the project’s construction to occur below ground, which reduces disruption to city streets neighborhoods and businesses compared to other tunneling methods. This approach also reduces the footprint needed for station construction,” said VTA in a news release.
VTA is one of the first transit agencies in America to use a single-bore tunnel design for transit. Projects in Spain, France, Dubai and the Netherlands have all used the process.
VTA says as the project moves forward, the agency continues to refine its construction plans, taking into account the latest innovations in the transit industry.
“Most recently, in 2022, the Tunnel and Trackwork Contractor proposed a new tunnel configuration that would reduce the cost of construction while improving passenger experience. The resulting design is a slightly larger tunnel that accommodates side-by-side tracks throughout the alignment, with center platforms at the stations. This new design will provide consistent and intuitive circulation for passengers at all three new underground stations,” read a recent VTA news release.
If all goes well, the boring process will begin in early 2025.