AUSTRALIA: Sydney’s Western Harbour Tunnel has entered its final 1.5km harbour-boring phase after the second 4,350t TBM, Barangaroo, joined Patyegarang, while tunnel fit-out and North Sydney connection works continue in parallel ahead of the planned 2028 opening.

Sydney’s Western Harbour Tunnel enters its final 1.5km harbour drive with both giant TBMs active as fit-out continues toward a 2028 opening.
Photo: Sydney Metro

The NSW Government announced Barangaroo’s start on August 11 after launching the machine 44.7m below Birchgrove Oval. Patyegarang had begun tunnelling on June 12, putting both machines onto the remaining section from Birchgrove beneath Sydney Harbour toward Waverton. Together, they are to excavate the last 1.5km of the 6.5km Western Harbour Tunnel.

That changes the project’s tunnelling status in a specific way: both bores across the remaining harbour section are now active. It does not mean the motorway tunnel is close to finished. Transport for NSW is already fitting out completed sections while the TBMs advance, and the latest NSW update says the Berry Street on-ramp in North Sydney is nearing completion.

What the final 1.5km harbour drive involves

Transport for NSW said before the launches that the two TBMs would start slowly and advance by around 11m a day when fully operational. That figure is a planned operating rate, not a reported current speed. The machines will work around the clock at depths of up to 50m below sea level.

As the twin drives progress, crews will also create cross passages roughly every 130m to connect the two tunnels. Transport for NSW says remote-controlled rock breakers will carry out this work progressively behind the TBMs, with each cross passage taking about three weeks to complete.

The lining operation is substantial in its own right. The project expects the two TBMs to install around 13,000 precast concrete segments and 1,300 culverts weighing 20t each, manufactured at a dedicated facility in Emu Plains. The latest government update does not give an updated breakthrough date for either machine, so the start of both drives should not be converted into an unsupported completion forecast.

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Purpose-built slurry TBMs add a second engineering story

Barangaroo and Patyegarang are purpose-built slurry TBMs developed by contractor ACCIONA with Chinese manufacturer CREG. Each has a cutterhead about 15.7m in diameter and weighs 4,350t. The NSW Government describes them as the largest TBMs ever assembled underground and the largest used in the Southern Hemisphere.

Their supporting equipment is designed for the harbour geology as well as the machines’ scale. Underground slurry-treatment plants can supply up to 3 million litres of slurry per hour to each TBM face, helping keep the excavation face stable in soft marine sediments before the slurry is filtered and reconditioned and excavated material is separated out.

ACCIONA also says the machines use robotic systems for cutter-disc replacement, removing the need for personnel to carry out that task in hyperbaric conditions, while additional robots assist with preparing tunnel segments for installation. Both TBMs were assembled and launched from underground chambers, a method ACCIONA describes as an Australian first.

Final tunnelling is running alongside tunnel fit-out

The harbour drive is therefore only one of several active workstreams. In May, Transport for NSW reported that more than half of the civil fit-out of tunnels and cross passages between Lilyfield and Birchgrove had been completed, with mechanical and electrical fit-out already under way. The civil package includes drainage, power, lighting, ventilation, road signs, fire-safety measures, tolling and Intelligent Transport Systems.

By August, the NSW Government said mechanical and electrical work was progressing on lighting, traffic-monitoring cameras and signage, while the Berry Street on-ramp was nearing completion. These works show why “final stage of tunnelling” and “final stage of the project” are not the same thing.

When complete, the Western Harbour Tunnel will connect the Warringah Freeway at North Sydney with WestConnex at the Rozelle Interchange. The government continues to say the tunnel is on track to open to traffic in 2028, but its latest update does not publish a detailed commissioning timetable. For now, the August milestone is best read as the point at which both giant TBMs have entered the project’s last harbour excavation section while fit-out and connection works continue around them.

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