The transit agency will issue a "Notice to Proceed" to Shimmick Construction Company Inc./Scanska USA Civil West California District Inc. Joint Venture that will allow them to start work on the subway section of the 5.4-mile extension in the fall.
BART Board President Thomas Blalock said the contractor's bid for the subway section was $136 million, which is 45 percent below the transit agency's estimate of $249 million.
The job, which is the first contract of a two-contract project, is for the construction of the underground phase of the extension.
BART officials expect to advertise for a bid later this year for the second contract, which is for above-ground elements, including the line, trackwork, station and systems. It's expected that the construction will start next year.
BART officials say they anticipate that the construction work will take about three and a half years and the new station will open for business in 2014.