Beginning with the initial stage of excavation, work has begun to carve out 1.7 kilometres of mainline tunnels between Rozelle and Birchgrove.

Natalie Ward, the Minister for Metropolitan Roads, noted that this marked a critical turning point in the construction of Sydney's historic third harbour crossing.

“Major construction has now commenced on the Western Harbour Tunnel – one of the most significant transport infrastructure projects being delivered in Sydney,” Minister Ward said.

“This really is a historic moment for our city. It was 90 years ago that construction completed on the Sydney Harbour Bridge, and 30 years since the Sydney Harbour Tunnel opened. Today, construction is commencing on Sydney’s third harbour crossing.

“Once complete, this important new connection will change the way commuters move across the city, taking pressure off key transport arteries including the Harbour Bridge and Tunnel, Anzac Bridge and Western Distributor.

“Our government is delivering projects that make it faster, easier and safer for commuters to move around our city as part of our $110 billion infrastructure investment pipeline.”

The 6.5-kilometer tunnels under Sydney Harbour that make up the Western Harbour Tunnel will connect WestConnex at the Rozelle Interchange with the Warringah Freeway in North Sydney.

Three lanes in each way will allow commuters to travel from North Sydney to Sydney Kingsford Smith Airport in up to 15 minutes less time.

Stage one of the Western Harbour Tunnel is being built by the John Holland CPB Joint Venture, which is simultaneously working on the Rozelle Interchange project.

This will minimise interruption to the local population and enable the Western Harbour Tunnel project to move into the major construction phase by utilising existing skills, equipment, and resources.

In late 2022, a construction contract will be issued to complete the second stage of northern tunnelling from Birchgrove across Sydney Harbour and onto North Sydney.