The VTA Is All in on 1 Tunnel to Connect San José By BART

South Bay transit officials in charge of building the $12.7 billion BART extension through downtown San José are doubling down on a single-tunnel design for the long-delayed megaproject, despite concerns from some engineering experts that conclusions made in a newly released report may lack “validity.”

Managers of the Santa Clara Valley Transportation Authority, which is building the 6-mile, four-station project for BART, say their plan to dig one of the largest underground tunnels on earth to house the train tracks and its platforms 80 feet below ground is still the best option.

They reaffirmed that determination on Monday, after the agency released what it called an independent cost, risk and impact analysis of a previously considered design that would use two smaller tunnels at a shallower depth — a more conventional approach to building subways in line with most of the existing BART system.

“This report was prepared in direct response to inquiries from our board of directors and reflects VTA’s ongoing commitment to transparency, fiscal responsibility, and thoughtful data-driven decision-making,” Carolyn Gonot, VTA’s general manager, said Monday during a press briefing on the analysis.

Tom Maguire, head of megaprojects for VTA, said the report highlighted a higher cost and additional time required to construct a twin-bore design.

“Changing the design of the BART Silicon Valley extension from its current single-bore back to a twin-bore design would increase the cost of the project by at least $600 million, and would not allow us to open the project any sooner than the 2037 date, which we are currently on track to deliver,” Maguire said.

In 2014, the project was expected to cost $4.7 billion, with an intended completion date in 2026.

Maguire said updating plans and environmental reviews for the original twin-bore blueprints that were partially completed in 2008 — when BART’s extension into Santa Clara County was first being planned — risks pushing back the project timeline even more. Building underground “boxes” to house stations around the two smaller tunnels would drive significant cost increases, he said.

The single-bore option would also be less disruptive, Maguire said, and requires less tearing up of surface streets like San José’s downtown thoroughfare, Santa Clara Street — as opposed to digging to build the shallower stations, or “cut-and-cover” construction.

The report, assembled by three different teams of VTA consultants, responded to critics, transit advocates and some VTA board members who say the twin-bore design might have been dismissed too quickly in 2018 by VTA because of concerns about the impacts of cut-and-cover construction.

However, a consultant for the VTA board’s project oversight committee, tasked with reviewing the report and offering feedback, questioned the agency’s conclusions and calculations about the twin-bore model.

Nasri Munfah, a principal at engineering firm Gall Zeidler, told VTA managers in a written memo that the cost estimate of the twin-bore design “appears to be overinflated” due to overly conservative timelines and nonessential design additions.

“These results invite questions of the validity of the cost estimate,” Munfah wrote in his response to the report.

Munfah wrote that the report fell short because it did “not compare the twin-bore vs the large single-bore concepts nor does it provide advantages/disadvantages of either of the two methods, or address risk assessment of either method.”

Barney Smits, a retired engineer who worked for BART for 25 years, told KQED the comments from Gall Zeidler are “right on target,” and said the VTA report seems “completely inaccurate.”

“They deliberately added things to the twin-bore design to make it more expensive and deliberately removed things from the single-bore design to try and make it look less expensive,” Smits said, of the VTA.

In a response, the VTA pushed back against much of Gall Zeidler’s critiques about project schedules, saying they “appear to be opinion-based rather than analysis-based.” The agency said its teams made “conservative but reasonable” assumptions in their analysis.

Gall Zeidler needed to include more “specific examples and details” to support concerns raised about the estimated cost of stations, the agency continued, and said VTA staff “takes exception to certain statements such as ‘overinflated’ and ‘questioning the validity.’”

As of Monday, the VTA said it isn’t planning to do any further analysis of the twin-bore design. It appears transit officials are hopeful this report will put to bed any skepticism of the agency’s decision.

Sudhanshu “Suds” Jain, a Santa Clara council member and a VTA board member, said Monday in an interview with KQED that he has “a great deal of skepticism” about the report, and is concerned overall about a lack of transparency from VTA higher-ups to the board and the public.

He said the project has been marred by questionable decision-making by VTA managers, such as waiting too long to ditch the project’s primary contractor earlier this year, which is expected to delay the start of tunneling by roughly a year and a half.

Jain also sits on the VTA board’s project oversight committee, which will review the report at its meeting on Thursday at noon.

Smits, the retired BART engineer, said the latest twin-bore report is “certainly not responsive to what the board and the public had requested,” and he expects the board members will have concerns with the way the report was prepared.

“The questions should continue,” Smits said, “because this report is not independent, it’s not a true apples-to-apples comparison.”