BART extension through South Bay takes step forward

Federal, state, and local officials break ground on the BART Berryessa Extension Project in San Jose on April 12, 2012. Federal, state, and local officials break ground on the BART Berryessa Extension Project in San Jose on April 12, 2012. Photo: Lance Iversen, The Chronicle Photo: Lance Iversen, The Chronicle Image 1 of / 25 Caption Close BART extension through South Bay takes step forward 1 / 25 Back to Gallery

The South Bay BART extension, now on its way to eastern San Jose, moved a step closer to tunneling beneath downtown toward Santa Clara, though funding remains uncertain.

The Federal Transit Administration has approved the second leg of what is known as BART Silicon Valley, allowing it to enter the project development phase of the federal funding program known as New Starts.

That means BART is nearer to competing for federal money needed for the 6-mile extension to Santa Clara.

BART trains now stop in central Fremont, but a 5.4-mile extension to Warm Springs, near the Santa Clara County line, is expected to open this summer. It was originally scheduled to open in December but ran into delays.

At the same time, workers for the Santa Clara Valley Transportation Authority are ahead of schedule on an extension that agency is building for BART that will travel south 10 miles from Warm Springs to the Berryessa neighborhood of eastern San Jose. It is tentatively scheduled to open in 2017.

The next section will take BART from Berryessa to downtown San Jose, where the trains will operate in a subway, and on to Santa Clara, where they will stop, above ground, near the Caltrain station.

The federal approval permits VTA to spend money on environmental studies. It also needs to finalize design, cost estimates and financial plans.

The extension from Berryessa to Santa Clara is expected to cost $4.7 billion, and VTA officials hope at least $1.1 billion comes from the New Starts program for major transit programs.

Even with that funding, however, the project would still need to come up with $2.4 billion. Santa Clara County officials are eyeing a November ballot measure that would raise the transportation sales tax to help pay for the extension.

Michael Cabanatuan is a San Francisco Chronicle staff writer. Email: mcabanatuan@sfchronicle.com Twitter: @ctuan