The latest update on the BART-to-San Jose project of course comes with more cost overruns and time delays, but transit officials say a single-tunnel design would involve fewer cost overruns and time delays than a double-tunnel design.

It’s hard to get excited over the BART-to-San Jose extension, simply because last we heard, it would not be finished until the year 2034 (and at a cost of $9.1 billion, while BART simultaneously claims to be going over a “fiscal cliff”). The planning is being primarily handled not by BART, but by Santa Clara County’s Valley Transportation Authority (VTA). That agency had a Monday press conference, and the Chronicle reports from that conference that we are now looking at a $12.7 billion project that won’t be finished until 2037.

Nonetheless, construction began in July on what they call Phase II of the BART to San Jose project. Phase I was the Berryessa/North San Jose station that opened in June 2020. As you see above, the Phase II project is four new stations that go all the way to Santa Clara, though there would be no straight-shot from SF to San Jose. That is, you’d have to take an East Bay train that goes to that Berryessa station rather than down the western Peninsula through San Mateo/Santa Clara counties.

And the VTA appears to be settling on a “single bore” tunnel design that’s one big tunnel, unlike the two-tunnel system you see at most SF and Oakland stations where trains go in both directions through separate tunnels. That (theoretically) means less disruption to the city of San Jose, with the streets being torn up for a shorter duration while crews build the tunnels.

At Monday’s press conference, VTA general manager Carolyn Gonot said this was “a principle we’ve long stood by: The single-bore tunneling method remains the most efficient and cost-effective approach to extend BART service into the heart of Silicon Valley.”

Though that method has its drawbacks too, because the tunnels need to run twice as deep underground, which means a lot of stairs and some disaster-situation concerns. Moreover, the Chronicle points out that VTA officials did not mention Monday that an engineering analysis said the cost of the two–tunnel system was wildly inflated, and it likely would not cost as much as VTA says.  

VTA officials dispute the claim that they had their cost estimates wrong.

“It was good to have a critique of the work, (which) helped us sharpen it up,” VTA chief megaprojects delivery officer Tom Maguire told the Chronicle. “But ultimately, the same standards we applied to our own cost estimates for the single bore were applied to the twin bore.”

Still, like the Van Ness Avenue bus lanes and the Chinatown Central Subway station, this thing will take years and years to complete. Don’t get us wrong: BART to San Jose is a long-overdue idea. The Chron notes that there’s a new plaza at Diridon Station, and Google has a new “mega-campus" planned for the area. And surely many people would take BART to concerts and 49ers games in Santa Clara if given the chance.

But if we’re talking about the year 2037… will there still be a Google by then? Will the 49ers even still play in the Bay Area at that point? These are the complications that could alter the course of a project if it’s not even expected to be finished for at least another 12 years.

Related: Text Messages Show San Jose Officials Tried to Bury Alleged BART-to-San Jose Cost Overruns [SFist]

Image: VTA