The $4.1 billion transit hub, dubbed the "Grand Central of the West," will replace the old Transbay Transit Terminal at Mission and First streets. The old terminal was built in 1939 and declared seismically unsafe after the Loma Prieta earthquake in 1989.
The new transit center will act as the terminus station for the planned high-speed rail system between San Francisco and Los Angeles, as well as a hub for 11 other transit operators -- Caltrain, AC Transit, BART, Golden Gate Transit, Greyhound, the San Francisco Municipal Railway, San Mateo County Transit District, Western Contra Costa Transit Authority, Lynx, Paratransit and Amtrak.
The first phase of construction, which includes the construction of a five-story transit center and new bus ramps, is scheduled to be completed in October 2017.
Demolition, the first stage of phase one, is expected to be finished by the end of this month and the second stage is already under way, said Robert Beck, a senior project manager for Transbay Joint Powers Authority.
The second stage -- the installation of shoring -- will allow crews to de-water and excavate the site. Construction crews will also begin construction of a buttress inside the shoring for stability at the end of this month. The buttress is expected to take 18 months to complete.
Construction of the center's below-grade structures -- such as the rail levels, which will serve Caltrain and the high-speed rail -- is set to begin in late 2012.
Phase two of construction will extend Caltrain's rail line from Fourth and King streets underground to the transit center.
Once finished, the transit center is expected to serve more than 100,000 passengers each weekday and more than 45 million passengers per year.