The WHT is a major transport infrastructure project that will make it easier, faster and safer to get around Sydney. By creating a western bypass of the Sydney CBD, the WHT will take pressure off the Sydney Harbour Bridge, Sydney Harbour Tunnel, Anzac Bridge and Western Distributor corridors to improve transport capacity in and around Sydney Harbour. The Western Harbour Tunnel is being delivered in two stages. The northern section of the tunnel, Stage 2, will be delivered by Acciona Construction Australia. This stage of the Western Harbour Tunnel sees early work construction expected to start in 2023. Stage 2 includes connections from Stage 1 at Cove Street, Birchgrove, to the Warringah Freeway near North Sydney, and complete tunnel fit-out.
The tunnel project will be built using two Tunnel Boring Machines (TBMs) to tunnel through clean sandstone under Sydney Harbour, while roadheaders will excavate the clean sandstone on the north side of the Harbour. Using the TBMs will eliminate any dredging activities through the Sydney Harbour seabed, removing risks to the marine environment and biodiversity and the need for construction sites at Yurulbin Point and Berrys Bay, significantly reducing construction impacts for thousands of residents in Birchgrove and Waverton. Once all excavation activities are finished, the roadheaders will be removed from the two northern tunnelling construction sites and the TBMs will be disassembled and removed in pieces. The larger parts of the TBMs that cannot be removed will be buried underground allowing for the mechanical and electrical (M&E) work to fit out the tunnels with lighting, safety features, and jet fans to proceed.