Local, state and federal officials on Tuesday watched as a large yellow backhoe clawed into old postal truck bays behind the historic Union Depot in St. Paul. The demolition, which makes room for future rail tracks, marks the beginning of major work to restore the Lowertown building to a regional transportation hub.

The plan: The vision is that light rail, passenger rail, bus lines, taxis, bicycles and pedestrians will all converge at the depot. It's the last stop for the planned Central Corridor light-rail line, a $957 million project that is expected to be completed in 2014. Amtrak and Greyhound have expressed interest in moving to the depot, as well.

The place: The block-long neoclassical building, owned by Ramsey County, faces 4th Street and sits between Wacouta and Sibley Streets in Lowertown. The rear concourse will serve as a waiting area and lead to the various transportation lines. In all, the site will encompass 33 acres, almost a third of the downtown riverfront.

The pricetag: The construction contract approved by the Ramsey County Regional Rail Authority was for $149 million. Overall, including acquisition, the project will cost about $243 million. The money comes from county, state and federal sources.

The players: Mortenson Construction is the lead contractor and will work with HGA Architects and Engineers and URS, a transportation and engineering design firm. Officials estimate the project will create 1,200 construction jobs.

The timeline: Work is expected to be completed in late 2012.

The past: The Union Depot was built between 1918 and 1923 on the site of an earlier train station that burned in 1915. The last passenger train left the station in 1971. The depot was put on the National Register of Historic Places in 1974.