The Sydney Metro Northwest project involved the construction of a rapid transit link to the north-western suburbs of Sydney. The link connects the suburbs of Rouse Hill and Chatswood via Castle Hilland Epping. The project was managed by Transport for NSW through its Sydney Metro agency. This project also involved railway construction in existing tunnels. The twin tunnels between Epping and Kellyville are the longest rail tunnels in Sydney, at 15.5 km long. They are also the deepest tunnels in Sydney hitting 67 m below ground level at the deepest point. This project, which included the conversion of the existing Epping to Chatswood Rail Link to metro standards, opened to service on 26 May 2019 as the Metro North West Line. GM Rail was engaged to work through a range of defects including poor workmanship by other contractors on the viaduct.
