The construction budget for the new Transbay Transit Center, pictured in August 2016, could grow by $200 million to avoid impacting nearby merchants. (Ryan McNulty/2016 Special to S.F. Examiner)

Transbay Transit Center downtown extension may cost $200 million more

The multibillion dollar tunnel set to serve the new Transbay Transit Center, known as the “Grand Central Station of the West,” may become far more expensive.

Instead of excavating from the street down into the new tunnel from Mission Bay to downtown, which is a construction technique called “cut and cover” and would potentially hurt merchants all along the route, much of the tunneling may instead be achieved by boring machines.

The catch, however, is that it would be costly to do.

Swapping out a cut-and-cover technique for the tunnel’s entrance, or “throat,” may stretch the budget upward of $200 million, Mark Zabaneh, executive director of the Transbay Joint Powers Authority, told the San Francisco County Transportation Authority board Tuesday.

The cost jump was revealed at the SFCTA board’s regular meeting, where transportation officials expressed optimism that less-impactful construction may be possible for the Phase 2 of the tunnel.

The project is overseen by the Transbay Joint Powers Authority, which is comprised of representatives from the San Francisco Municipal Transportation Agency, the Mayor’s Office, the Board of Supervisors, AC Transit and Caltrain.

“I’m reluctant to share costs, it’s a preliminary number,” Zabaneh cautioned. “We need to do a little more vetting.”

Indeed, outside the meeting, Zabaneh told the San Francisco Examiner that the cost was likely on the low side.

The $200 million number is also close to the amount — $260 million — that San Francisco already spent on a bailout for Phase 1 of the project in May 2016, after it was discovered multiple errors sent project costs soaring to $2.259 billion.

Initially, Phase 1 of the project was set to cost $1.189 billion.

Supervisor Aaron Peskin, who serves as chair of the SFCTA board, recalled this bailout when told of the potential skyrocketing costs of the downtown extension tunnel.

“The elephant in the room is we borrowed a significant amount of money from Phase 2 to pay for the Transbay Terminal in Phase 1,” Peskin told the board.

Peskin also said there must be a less disruptive construction process, which the spiraling expense may achieve. He warned against turning downtown streets into “an open pit for four years … so we do not eliminate a neighborhood that is vibrant.”

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