After years of planning and months of assembling one of the largest machines ever used in South Australia, tunnelling is now underway on the $15.4 billion River Torrens to Darlington (T2D) project to deliver a non-stop South Road.
The start of tunnelling marks a significant milestone for the state’s largest infrastructure project, with tunnel boring machine (TBM) Mary now beginning to excavate the first 4.5-kilometre Southern Tunnel from the Southern Precinct at Clovelly Park to Glandore.
Operating 24/7, Mary will progress approximately 8-10 metres per day, with up to 20 specialised workers inside at any one time as she embarks on South Australia’s first major underground road tunnelling project.
Mary’s first components arrived in Adelaide in October 2025 and since then, piece by piece, each component has been lifted into the launch box by a 500-tonne gantry crane before being assembled into the mega machine now carving out a non-stop South Road.
Measuring approximately 100 metres in length, 15 metres in diameter and weighing 3,500 tonnes, 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.
Named after pioneering South Australian suffragists Mary Lee, Catherine Helen Spence and Elizabeth Webb Nicholls, the project’s three TBMs recognise the trailblazers who helped shape South Australia.
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.
The T2D project is the final 10.5-kilometre section of the North-South Corridor, and will complete 78 kilometres of non-stop, traffic light-free motorway between Gawler and Old Noarlunga.
The Australian and South Australian Governments have each committed $7.7 billion towards the project.
With tunnelling now underway, the community can follow Mary’s journey using the new online TBM Tracker. The tracker will provide regular updates on each TBM’s approximate location and other key information, with updates on Catherine and Elizabeth available once they begin tunnelling.
“This is a momentous occasion for the largest ever infrastructure project in our state’s history,” said Premier of South Australia Peter Malinauskas.
“After all the careful planning and machinery assembling, tunnelling is now underway to deliver South Australia a non-stop South Road.
“The scale of this project is extraordinary and I’m proud to be leading a government delivering such important infrastructure works for South Australia.”
Federal Infrastructure, Transport, Regional Development and Local Government Minister Catherine King was excited by the prospect of the project connecting Adelaide’s north to south.
“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,” she said.
“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.”
The TBM works on T2D project is being delivered by the T2D Alliance, a five-firm consortium consisting of John Holland, Bouygues Construction, Arcadis Australia, Jacobs, and Ventia.
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