Newtrain tunnel part of multimillion-dollar study

Agency OKs $3.27 million for Transbay Terminal

Trains departing from the future Transbay Terminal may travel on an underground route below the Embarcadero as they make their way to the Peninsula under a new proposal that’s being studied.

Last week, the San Francisco County Transportation Authority unanimously voted to allocate $3.27 million to study an update to the original design that would include a loop-shaped train tunnel. The configuration would allow trains to travel continuously in one direction without having to reverse before heading out to a destination.

The authority is charged with allocating funds from Proposition K, which voters passed in November of 2003. The half-cent sales tax pays for transportation programs.

The long-awaited Transbay Terminal project calls for transforming the dilapidated bus hub at Mission and First streets into a world-class transportation center for Caltrain, several bus lines, BART and high-speed rail originating from Los Angeles.

The cash-strapped $3.4 billion project, slated to begin in 2008 and be completed by 2021, includes electrifying Caltrain and bringing the Peninsula commuter line underground to downtown from its current terminus at Townsend and 4th Street, near AT&T Park.

Plans call for a 1.3-mile tunnel from 4th and Townsend streets ending in a tail or spur-shaped configuration east of the Transbay Terminal under Main Street.

That configuration would mean trains couldn’t turn around except by reversing on the same track.

“Logically, trains run in a loop,” said Richard Silver, executive director of Rail Passenger Association of California. “As a practical matter the train is going to dwell there for a while (before it can change direction and start moving again). So a loop is a good idea.”

Members of the Transbay Joint Powers Authority Board, San Mateo Supervisor Jerry Hill and Michael Cohen from Mayor Gavin Newsom's office, said the study of the loop track is a good idea since it could reduce costs and make the design more efficient.

Initial reports presented to the transit authority show that the train loop configuration could save $200 million, in part because it provides room for four tracks, instead of the six proposed under the stub or spur configuration.

A panel of experts convened this Spring to discuss plans for the terminal, when the idea of closing the loop emerged, said Rodney Pimentel, the authority's deputy director for capital projects.

Still, the new plan calls for increasing the length of the tunnel by a mile to 2.3 miles, and the route — from Transbay Terminal, south along the Embarcadero, west along Townsend Street and back to Second Street — and then down Fourth and Townsend streets, has yet to be studied.

The study, which includes everything from geotechnical engineering to boring holes below the Embarcadero — could be complete in March.Construction of the tunnel would likely begin around 2012 if the plans are approved.

mcarroll@examiner.comBay Area NewsLocal

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