FREMONT — BART is gearing up for its expansion into Fremont's Warm Springs district and farther south into Santa Clara County, officials said.

The transit agency has issued a request for bids to build a subway line under Fremont's Central Park — the first phase of the Warm Springs extension.

BART intends to start construction this summer on the $200 million subway line, which it expects to complete by the end of 2012. The entire $890 million, 5.4-mile Warm Springs extension that will bring BART to within walking distance of the New United Motor Manufacturing Inc. plant, as well as a proposed stadium for the Oakland A's, is scheduled for completion in 2014.

With the narrow approval of Santa Clara County's Measure B last year, transit planners are working to extend BART farther south to San Jose once the Warm Springs expansion is finished.

Fremont is also considering how it might fund a second station along the BART extension in the city's Irvington district.

New stations in Warm Springs and Irvington have long been touted as a way to relieve traffic on interstates 880 and 680, as well as open up new development opportunities around the stations.

However, given the dour economy, BART spokeswoman Luna Salaver touted the project as a catalyst for creating "a great number of jobs," although agency officials couldn't estimate how many jobs will be generated.

The BART extension will run from the Fremont station across a bridge spanning Walnut Avenue, before dropping below ground just north of Stevenson Boulevard. The track will run underneath Stevenson and Central Park and return above ground north of Paseo Padre Parkway. The route then continues across Paseo Padre, Washington Boulevard and Auto Mall Parkway to the new station site at Warm Springs and South Grimmer boulevards.

Stevenson Boulevard will lose a lane of traffic in each direction during construction periods, said Jim Pierson, Fremont's director of transportation and operations. All park facilities will remain open during the construction period, although the dog park, basketball courts and some parking spaces will be relocated.

Fremont reporter Matthew Artz can be reached at 510-353-7002 or martz@bayareanewsgroup.com. Read his blog posts at www.ibabuzz.com/tricitybeat.