The San Francisco Municipal Transportation Agency (SFMTA) awarded a contract worth USD 233M to a joint venture of SA Healy and Barnard on 28 June for the Central Subway extension.

Underground construction includes two single-track tunnels of 1.7 miles (2.7km), which will be excavated by two TBMs of 6.4m diameter and will include a one-pass precast segmental lining.

The Central Subway extension will provide rail services to Chinatown and connect to existing commuter rail lines BART and Caltrain.

There are three underground station contracts yet to bid in late 2011 or early 2012. The fourth station will be surface level.