Mega Machines Head Under Yarra In Final Tunnelling Push

12 metres under the bed of the Yarra River is a 1,100 tonne tunnel boring machine (TBM) with a second machine not far behind, as they both excavate the final few hundred metres to complete the section of the Metro Tunnel Project’s twin tunnels between South Yarra and the CBD.

Minister for Transport Infrastructure Jacinta Allan today toured TBM Millie, meeting the team of tunnellers who work day and night on the massive machine. Millie will take around two weeks to tunnel the 120 metres under Melbourne’s iconic waterway, as life on the Yarra for rowers, boaters and sightseers carries on undisturbed. Ms Allan told reporters, “Tunnelling on the Metro Tunnel Project is heading into its final stages, with a TBM now digging under the Yarra, as it completes this incredible feat of engineering deep under Melbourne’s CBD.”

After crossing under the river, Millie will dig a further 300 metres to Town Hall Station below Swanston Street to complete the final section of tunnel in the south-east, followed a few weeks later by TBM Alice.

Geological and environmental testing has shown that ground conditions deep under the Yarra include silt, gravel and basalt. The Metro Tunnel TBMs have encountered a variety of ground conditions when tunnelling in other sections of the project.  

Tunnelling is now 85 per cent complete, with TBM Joan now digging more than 30 metres below Swanston Street towards Town Hall Station from the State Library Station site in the CBD’s north, and TBM Meg to be launched in coming days. The arrival of all four TBMs at Town Hall Station later this year will mark the end of tunnelling to create the twin 9km-long, 6.3m-high rail tunnels from Kensington under the Melbourne CBD to South Yarra.

Each 120-metre-long TBM is equipped with a state-of-the-art navigation system to ensure they dig accurately along the tunnel alignments. They are staffed and monitored 24 hours a day, seven days a week, and equipped with an office, kitchen and toilets.

The Metro Tunnel will have two CBD stations: Town Hall Station at the southern end of Swanston Street, with entrances at Federation Square, City Square, and the corner of Flinders and Swanston streets; and State Library Station at the northern end of Swanston Street, with entrances near Franklin Street and La Trobe Street.

These two new CBD stations will allow Metro Tunnel passengers to connect to City Loop services via underground pedestrian links at Flinders Street and Melbourne Central stations. At 19 metres wide, the Town Hall and State Library station platforms will be among the widest underground metro platforms in the world, ensuring plenty of space for the thousands of passengers who will use them every day.

Town Hall Station will be a gateway to some of Melbourne’s most popular landmarks, including Federation Square, St Paul’s Cathedral and the Arts Centre, and the surrounding precinct will be transformed to take advantage of nearby laneways and revitalise the City Square.

Ms Allan said, “We’ve almost got 18 kilometres of concrete-lined tunnel, while five new stations are taking shape underground with walls, roofs and platforms now being built – as we continue on the path to more trains, more often.”

The State Government said Metro Tunnel Project will create additional capacity for more than half a million passengers a week during peak periods.