en.Wedoany.com Reported - ACCIONA has commenced the final tunnelling phase of the New South Wales Government's Western Harbour Tunnel project in Australia, with tunnel boring machine (TBM) Patyegarang starting excavation beneath Sydney Harbour on June 12.
Excavation began at a depth of 44.7 metres below Birchgrove Oval, with Patyegarang advancing towards Waverton, marking the final stage of underground excavation for the project.
New South Wales Minister for Roads Jenny Aitchison stated that this is a significant milestone for the Western Harbour Tunnel project, marking the beginning of the final phase of excavation beneath Sydney Harbour. Assembling these giant machines entirely underground is an extremely complex task, and the team has performed exceptionally. Building and operating the slurry treatment plant for the tunnel boring machine underground is not only a major win for the local community but also a first in Australian and even global engineering history.
Patyegarang and its sister TBM Barangaroo each have a diameter of 15.7 metres and weigh approximately 4,350 tonnes, making them the largest tunnel boring machines ever assembled underground in the Southern Hemisphere. Both machines are designed to handle the complex geological conditions beneath the harbour. The second TBM, Barangaroo, is currently 94% assembled and is expected to begin excavation in about four weeks. As excavation progresses, the machines will install approximately 13,000 precast concrete segments to line the excavated tunnel.
Supporting the excavation work is a fully underground slurry treatment plant, designed to minimise local disruption. The plant, over 100 metres long and 15 metres high, is one of the largest underground facilities of its kind ever assembled and operated. It is designed to pump up to 3 million litres of slurry per hour to each TBM to maintain tunnel stability. The plant separates rock material from the slurry, which can be recycled for other projects, and returns the treated slurry mixture to the TBM.
These TBMs, named after prominent Indigenous women, will operate around the clock, with approximately 40 people per machine per shift. Together, they will excavate the final 1.5 kilometres of twin tunnels beneath the harbour, reaching depths of 50 metres below sea level. Upon completion, the 6.5-kilometre Western Harbour Tunnel will connect the Warringah Freeway near North Sydney with the WestConnex M4 and M8 at the Rozelle Interchange, allowing vehicles to bypass the central business district. The route is designed to relieve pressure on existing cross-harbour traffic corridors, including the Sydney Harbour Bridge, Sydney Harbour Tunnel, Anzac Bridge, and the Western Distributor corridor.
This new motorway is the first cross-harbour road built in Sydney in over 30 years and is scheduled to open in 2028. The project is divided into two phases. Phase one, carried out by the John Holland CPB Contractors joint venture (JHCPB), involved excavating over 1.7 kilometres of traffic tunnels from Emily Street in Rozelle to Cove Street in Birchgrove, completed between June 2022 and February 2025. In phase two, ACCIONA was awarded the contract in December 2022, covering 4.8 kilometres of tunnel excavation from Birchgrove to Cammeray. This phase also includes the connection from Cove Street in Birchgrove to phase one, extending to the Warringah Freeway near North Sydney, excavation beneath Sydney Harbour, and complete tunnel interior fit-out.
In June 2026, the Planning, Housing and Infrastructure department approved Part 2 of the Western Harbour Tunnel Place, Design and Landscape Plan (PDLP) for Berrys Bay. This plan defines the final parkland design for the area. It incorporates community and stakeholder feedback received in mid-2025 and was developed in collaboration with North Sydney Council, particularly to realise the vision for the Woodley's Shed community pavilion. The PDLP also specifies measures for play spaces, native landscaping, and the integration of heritage and cultural elements into the parkland.
