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VTA is again changing its plans for the multi-billion-dollar project bringing BART

VTA is again changing its plans for the multi-billion-dollar project bringing BART through downtown San Jose, dropping a proposal to bore the world’s largest subway tunnel for nearly five miles beneath the city and reopening the process for designing an extension that is already severely delayed.

What remains unclear, though, is how much this redesigned version of the project will cost, or when BART trains will finally roll into the center of the Bay Area’s largest city.

Critics had raised questions about VTA’s ability to pull off San Jose News audacious plans to bore a 55-foot-wide tunnel under downtown San Jose, particularly as the agency is nearly two years late delivering stations in Milpitas and Berryessa — the far more conventional first phase of the long-awaited Santa Clara County extension it is building for BART.

VTA arrived at the massive downtown San Jose tunnel design following several years of discussions and a series of concessions to businesses, which wanted the agency to minimize disruptions from the project at street level, and to BART leaders, who had resisted a plan to bore a smaller tunnel with station platforms stacked on top of one another.

VTA officials earlier this year said the 55-foot-wide tunnel design was not riskier than other subway building methods, and downplayed the idea that it was adding to the project’s overall cost, even though that tunnel was substantially larger than prior plans for the project. A VTA spokeswoman also said that contractors at the time had not raised any concerns about the designs.

But on Friday, VTA officials leaders said that prospective contractors who were initially supportive of the project became more skeptical of it as the design process continued.

The tunnel design the agency’s staff spent a year pursuing is some $4 billion more expensive than initially believed and substantially riskier than other designs, General Manager Nuria Fernandez told the agency’s board.

“The risk was too much and we were not certain that we would be getting bids,” Fernandez said, “and if we did get bids to build this configuration they would be much higher than what we had budgeted.”

VTA engineers will now explore two competing ideas for revising Press Release Distribution Service In San Jose the design that involve smaller tunnels and stacked station platforms — with BART officials’ approval. VTA’s board will pick a new design later this year.

It will take several months of further design work to figure out how much the project will cost or a schedule for construction, Fernandez said. The most recent estimate for it was $5.6 billion, with construction starting in 2022 and stations opening in 2029 or 2030.

The agency’s planners won’t be starting from square one with the new designs. They will work within a design framework that has already gotten environmental clearance, and will keep the extension’s route the same: Trains will continue south from the Berryessa station before diving underground, turning across Highway 101 and running west beneath Santa Clara Street, then continuing north from Diridon Station to a final stop in Santa Clara.

Both of the new design ideas call for using, at least for part of the extension, a smaller version of the “single-bore” tunneling concept that VTA officials chose for the project in 2018.

In that method — which was pioneered by a Spanish subway line and is unprecedented in North America — subway platforms and both directions of tracks are all contained within a single tunnel. Unlike more conventional subway designs that involve boring two smaller tunnels with “cut-and-cover” station construction that tears up streets for years at a time, the method is much less disruptive at ground level.

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