The Santa Clara Valley Transportation Authority says it needs another three months to finish a design for its single bore tunnel option for San Jose’s BART project.
The request is part of the ongoing issue of whether BART trains should traverse downtown San Jose through one or two tunnels.
The $4.7 billion project will extend BART about six miles — from the new Berryessa station to central San Jose.
While a panel of experts favors two tunnels, VTA says a one-tunnel project would be faster, cheaper and less disruptive to pedestrians and traffic. It would cut 10 months off the four-year tunneling phase and reduce costs by $50 million, according to VTA.
But the one-tunnel design has not been as widely used as the bores with two tunnels.
Last month, it seemed that the issue was close to being settled. But the panel of experts agreed at a mid-November meeting that issues of fire and safety needed to be better addressed.
The panel’s conclusions mean that more time is needed, VTA spokeswoman Brandi Childress wrote in a post on the agency’s website.
“VTA will extend the project development timeline to demonstrate more thoroughly how the single-bore configuration can satisfy BART’s operational safety concerns,” she wrote.
VTA also is exploring how to reduce the impact of construction, according to the statement.
VTA needs three more months to work on San Jose BART tunnel plan