South Australia’s River Torrens to Darlington project has hit its most significant milestone yet, with the first tunnel boring machine beginning to excavate
Tunnelling is now underway on South Australia’s $15.4 billion River Torrens to Darlington (T2D) project, which will deliver a non-stop, traffic light-free South Road in Adelaide.
Tunnel boring machine (TBM) Mary is beginning to excavate the first 4.5-kilometre Southern Tunnel from the Southern Precinct at Clovelly Park to Glandore.
Operating 24 hours a day for seven days a week, TBM Mary will progress approximately eight to 10 metres per day, with up to 20 specialised workers inside at any one time as it embarks on South Australia’s first major underground road tunnelling project.
“As we reach another important milestone for the River Torrens to Darlington project, we are a step closer to taking thousands of cars off local roads, making it safer and faster for commuters travelling across the state,” federal infrastructure minister Catherine King says.
“Once finished, the project will complete 78 kilometres of non-stop motorway between Gawler and Old Noarlunga and allow motorists to avoid 21 existing sets of traffic lights between the River Torrens and Darlington.”
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TBM Mary’s first components arrived in Adelaide in October 2025. Since then, each component has been lifted into the launch box by a 500-tonne gantry crane before being assembled.
Measuring approximately 100 metres in length, 15 metres in diameter and weighing 3,500 tonnes, TBM Mary is one of three large-scale TBMs being used on the T2D project.
The project’s second TBM, Catherine, will soon launch from the Southern Precinct to excavate the second parallel 4.5-kilometre Southern Tunnel. Further north, the third TBM, Elizabeth, will launch from the project’s Central North Precinct at Hilton to construct the 2.2-kilometre Northern Tunnels.
The use of three TBMs allows both the Northern and Southern Tunnels to be constructed concurrently, helping deliver a non-stop South Road by 2031.