UNION CITY -- It's one down and several more to go for Union City's drive to develop an urban core and transit hub.

Officials from across the Bay Area converged on Union City's BART station Thursday to celebrate completion of the first phase of a new urban district that is slated to one day include two residential towers, office buildings and a fully redesigned BART station that also will serve several regional commuter rail lines.

"We see this as a great combination where jobs, housing and transit are coming into one area," Mayor Mark Green said.

While the entire project still is years from completion, the city is celebrating a major expansion of its BART station, which will be needed to accommodate increased ridership when other commuter rail lines establish service there.

The $47 million expansion includes a pedestrian promenade, new escalators and staircases, expanded parking, a glass facade and a 700-foot-long bus canopy with solar panels to help power the station.

The next phase, expected to cost between $15 million and $30 million, will involve opening up the east side of the station to create a pass-through for riders to adjacent rail tracks.

The city hopes to have that completed by 2013, but first it needs regional authorities to acquire the track right of way from Union Pacific, officials said.

Once that happens, work can begin on routing regional rail lines along those tracks with a stop at the Union City BART station.

The likely first arrival will be Capitol Corridor, which runs from Sacramento to San Jose, Green said.

Union City also is counting on the station serving the proposed Dumbarton Rail, which would run trains from Union City, across the Bay to Redwood City and then to San Jose and San Francisco. However the line, which involves the construction of a rail bridge, has proved more expensive than originally anticipated, and won't be in place until 2020 at the earliest, Green said.

The Altamont Commuter Express also likely won't stop at the station until a rail bridge over the Bay is constructed, Green said.

While new rail service is still years away, high-density housing development already has started around the station. Avalon Bay recently constructed 438 apartments, and work has begun on a 157-unit affordable housing project directly east of the station.

In 2013, the San Jose-based development firm Barry Swenson Builder is scheduled to begin work on a project that involves two residential towers, expected to rise about 14 stories, and up to 973 housing units.

"Redevelopment is what made this whole thing happen," Union City Redevelopment Manager Mark Evanoff said. "The private sector alone couldn't have done this."