Two tunnel boring machines (TBMs) have relaunched from the Five Dock metro station site, as Sydney Metro West gears up for its biggest year of tunnelling.

The 1,300t machines know as Beatrice and Daphne are boring the next part of the project between Five Dock metro station and Burwood North station about 2km away.

The Acciona and Ferrovial joint venture is delivering NSW Government's Sydney Metro West’s central tunnelling contract. It involves building 11km of twin tunnels and five new stations at the Bays, Five Dock, Burwood North, North Strathfield and Sydney Olympic Park.

The TBMs arrived at Five Dock station in December 2023, in what was heralded as the first “double breakthrough” in the southern hemisphere.

They had bored a 4.3km section of the twin metro tunnels after being launched at the Bays site seven months prior.

The TBMs are tunnelling an average of 200m per week to build the 11km section of the new metro tunnels from the Bays to Sydney Olympic Park.

Before being relaunched, the mega machines underwent maintenance, including the replacement of gear boxes and cutter discs, to ensure safe operations during the next leg in the journey.

A total of six TBMs will be used carve out the 24km Sydney Metro West line between Sydney central business district (CBD )and Westmead.

Two other TBMs, Betty and Dorothy, are expected to make significant progress on building the tunnels between Sydney Olympic Park and Westmead this year. They were launched from the Clyde Stabling and Maintenance Facility site in the second half of 2023.

All four TBMs are expected to reach Sydney Olympic Park in 2024.

At the Bays station, the site is being prepared for the arrival of the project’s two remaining TBMs. These will be launched towards Hunter Street in mid-2024 to bore 3.5km of twin tunnels. They are expected to complete tunnelling in 2026.

A John Holland, CPB Contractors and Ghella joint venture is delivering the final major tunnelling on the project between the Bays and Hunter Street.

On other parts of the scheme work is also ramping up, with excavation of Sydney Metro West’s Hunter Street station now 30% complete.

Roadheaders – electric-powered tunnelling machines that have rotating heads fitted with metal picks to break and excavate rock - are being used to excavate the Hunter Street station cavern and turnback tunnels. Each machine weighs up to 120t.

The turnback tunnels to the east of the new station will allow trains to turn around before travelling back towards Westmead.

More than 149,000t of material has been excavated by the roadheaders so far, and the largest area of the cavern that has been excavated is 235m2.

Sydney Metro West is a new underground railway that will connect Greater Parramatta and the Sydney CBD.