At the special meeting held on October 17, 2025, the Board of Directors of the Santa Clara Valley Transportation Authority (VTA) - after hearing the presentation of the peer review conducted by U.S. tunnelling and transport experts, along with their recommendations - confirmed Scenario 1 as the preferred configuration for Phase II of the BART Silicon Valley Extension. The Board authorized further development of the design, contract definition, project implementation, financial planning, and the formulation of funding strategies, including the Federal Transit Administration (FTA) Full Funding Grant Agreement (FFGA).
Scenario 1 involves the construction of a 8 km (5 miles) long single-bore tunnel, with a diameter of approximately 16 meters (53 feet), at an estimated cost between EUR10.4 and EUR10.8 billion (approximately USD12.1 to USD12.5 billion), consistent with available funding.
Scenario 1A, which involves the simultaneous construction of two tunnels - one large (16 m / 53 ft in diameter) from the west and a smaller one (12 m / 40 ft in diameter) from the east - would cost about EUR690 million (USD800 million) more, while introducing additional risks and greater impacts on the Little Portugal and Downtown San José communities.
The peer review emphasized the importance of a strong VTA–BART partnership: both agencies agreed to reestablish regular contact and prioritize inter-agency communication.
Construction work at the West Portal/TBM launch site continues to advance with day and night work underway. Major activities include excavation for the launch structure, installation of bracing for support of excavation walls, drilling dewatering wells to manage groundwater, and installation of monitoring equipment. Stakeholder engagement and communication efforts are also continuing, including progress briefings and updates on upcoming activities.
Click here for the VTA working group meeting of November 6 and here for the VTA/BART working committee meeting of November 7.
Click here and us/61 for the tunnelbuilder archive and for further information please visit https://www.vta.org/ and https://www.vtabart.org/. 46/25.
