Panel favors two-tunnel option

SAN JOSE >> The issue of whether BART trains should traverse downtown San Jose through one tunnel or two is more than a month away from being settled, but a panel of experts has concluded that the former option — favored by the Santa Clara Valley Transportation Authority and city leaders concerned about impacts to businesses — is not the way to go.

Convened last week by BART and the VTA, the panel determined the single-bore option is viable, but it also identified “key operational considerations related to fire/life/safety that would need to be addressed in the design to better meet BART’s operating requirements,” VTA spokeswoman Brandi Childress wrote in a post on the agency’s website.

Specifics about those considerations and their related costs will be released in the coming weeks, she said in a follow-up email.

Looming deadlines to seek $1.5 billion in federal aid also factored into the panel’s recommendation, according to Childress. The $4.7 billion project ultimately aims to extend BART from the recently completed Berryessa station about 6 miles into central San Jose.

The VTA, which is building the tunnel or tunnels that will run below downtown, and city leaders concerned about the impact to businesses have expressed a preference for a single 45foot bore with two tracks. BART, which will operate the trains, favors two 21-foot tunnels with a single track in each — what it uses on its existing 112-mile system.

The twin-bore option would cause major impacts to Santa Clara Street between Market and Fourth streets during utility relocation and station excavation. Once the station is dug, the VTA would excavate an opening, move a 45-foot drill under the street and cover it with metal plates to keep traffic moving, a procedure known as “cut and cover.”

With a single bore, work often would be done on side streets adjacent to Santa Clara Street. The option could shave 10 months off the four-year tunneling phase, slash $50 million in costs and be less intrusive to pedestrians and traffic, according to the VTA.

The option favored by the VTA, however, has not been widely tested and its actual costs remain to be determined. The other is used globally and its costs are better understood.

“We all share a common goal of delivering the safest and most cost-efficient project we can, with as few impacts to our residents, businesses and neighborhoods as possible,” said Mayor Sam Liccardo, a proponent of the single-bore option, in a statement.

Liccardo said he looked forward to reviewing the panel’s detailed findings, as well as continuing “discussions with BART to determine the best option for constructing this critical extension of our public rail system.”

The VTA Board of Directors is expected to make a final decision on whether to build one tunnel or two when it meets in January.