During its August 26, 2022 presentation to the BART Board, VTA spokesperson Takus Salpeas put the width of the center-loading platform in the downtown San Jose station at 22 feet, about the same width as BART’s existing platforms in places like Castro Valley and Orinda. Under SF’s Market Street the platforms are 35 feet wide.
If a 22-foot platform requires a just-announced 53-foot diameter tunnel (up from the recently established 48-foot diameter tunnel), then a 35-foot platform would presumably require a 65-foot tunnel. Recently the Federal Transit Administration (FTA) put the cost of BART Phase II assuming a 48-foot tunnel at $9.15 billion. So the question becomes, how much would a 53-foot tunnel increase the cost of the project? Or a 65-foot tunnel?
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The VTA went on to contend that the twin-bore alternative would require difficult and costly cross-passages that would put BART riders at risk during emergencies. But cross passages are used in subways all over the world, including in most of, if not all of, BART’s existing subways. Maybe the VTA believes that BART’s other subway stations are unsafe.
During the meeting BART Director Ames appropriately requested an independent alternative analysis, including a cost estimate, of the twin-bore option. The VTA’s response was to dismiss the request saying that the twin bore option had been looked at and found wanting. They went on to claim that the single bore option would in fact actually reduce costs. (Anyone believing that line is a potential Golden Gate Bridge buyer). The VTA’s design consultant, Peter Kiewit/Shea/Taylor, (KST) responded in a more nuanced manner. In response to a question KST reported that “we spent a lot of time discussing the option but didn’t write any reports on the subject”. Probably meaning that the twin-bore option was ruled off the table by the VTA at the outset of the discussion. If such a study were undertaken, as it certainly should be, it appears that KST would be in the best position to look at the matter analytically and objectively.