熊谷組
Construction of the line started in February 2004. The contract for the line was awarded to a joint venture of John Holland, Macmahon Contractors and Multiplex. The contract for the city centre works, including the tunnels, was awarded to a joint venture of Leighton Contractors and Kumagai Gumi. The contractors used a tunnel boring machine manufactured by Mitsubishi Heavy Industries. The first tunnel was completed on 3 June 2006, and the second on 27 October 2006.