A cost report released by the Santa Clara Valley Transportation Authority (VTA) yesterday affirms a single-bore tunnel is the right approach for the BART Silicon Valley Phase II project (BSVII).
The detailed report analysing the cost of twin-bore tunnelling for BSVII was undertaken in response to questions raised by the VTA board of directors.
VTA general manager/CEO Carolyn Gonot said the report underscored that the VTA’s choice of a single bore was correct.
“The findings reaffirm that the single-bore approach remains the most cost-effective method to bring BART service into the heart of Silicon Valley,” she said.
A statement by the VTA said the board of directors and the community had consistently supported the single-bore design, recognising its advantages in minimising community disruption, reducing surface construction impacts, and delivering transit more efficiently.
Key findings of the report highlight higher cost for the twin bore because of the large cut-and-cover stations, challenging construction factors, and additional time required for design.
The report was commissioned as part of VTA’s ongoing commitment to provide accurate, data-driven information that informs decision-making and builds public trust.
“Our board has raised the question of whether a design change to the twin bore would be cheaper and safer. This report is a direct response to that question,” said Tom Maguire, VTA chief megaprojects delivery officer.
“It gives a clear picture of the costs involved with a twin- bore tunnel and reinforces why the single-bore approach remains the best choice for this project.”
