Ground was broken in February on San Francisco’s Central Subway.

The $1.6bn 2.7km long tunnel will form part of a new commuter line running north to south from Caltrain station to Chinatown on the Muni Metro light rail system. The tunnel will be excavated using TBM. Tunnelling is scheduled to begin in 2012.

The line was originally expected to be operational by 2016 but this date has now been pushed back to the end of 2018.

The Department of Transportation donated $948M towards the project. The rest of the funding will be made up of state and local dollars.

The groundbreaking ceremony took place beneath an Interstate 80 overpass, the location where the subterranean portion of the railway will begin.

San Francisco Mayor Gavin Newsom told reporters at the ceremony that the subway will reduce surface street congestion, will unite cultural centres around the city, as well as creating more than 40,000 jobs.

The client San Francisco Municipal Transportation Agency estimates that 76,000 people will use the subway daily by 2030.