William Street tunnel

The William Street tunnel is a railway tunnel under the central business district of Perth, Western Australia. Built between 2004 and 2007 as part of the construction of the Mandurah line, the tunnel connects the Mandurah line to the Yanchep line. The tunnel consists of a 690-metre-long (2,260 ft) twin bored section and a 1,158-metre-long (3,799 ft) cut-and-cover section. The tunnel has two stations: Perth Underground and Elizabeth Quay.

The construction of the Mandurah line was divided into eight contract packages. The William Street tunnel was part of Package F, also known as the City Project. The contract for Package F was awarded to Leighton–Kumagai Gumi in February 2004 for $324.5 million. Preliminary works began the same month. Tunnelling began in October 2005, starting from Elizabeth Quay station and heading north. Boring for the first tunnel was completed in June 2006, after which, the tunnel boring machine was transported back to Elizabeth Quay to dig the second tunnel. The second tunnel was significantly faster to bore, being completed in October 2006.

Construction was significantly disrupted by industrial action, which culminated in the prosecution of 107 workers for illegally striking in February and March 2006 following the issuance of a strike ban by the Australian Industrial Relations Commission. The strikes, along with complications involving heritage protection at Perth Underground station and engineering challenges on the foreshore, resulted in the tunnel's opening being delayed beyond December 2006. The first train entered the tunnel in August 2007, and the tunnel opened to passengers on 15 October 2007, ahead of the rest of the Mandurah line's opening on 23 December 2007.