Tunnelling offically underway on $15.4bn Torrens to Darlington Project

Tunnelling is now underway on the $15.4 billion River Torrens to Darlington (T2D) Project, after years of planning and months of tunnel boring machine assembly.

The start of tunnelling marks the most significant milestone for South Australia’s largest infrastructure project. Tunnel Boring Machine (TBM) Mary is now excavating the first 4.5-kilometre Southern Tunnel from the Southern Precinct at Clovelly Park to Glandore.

“This is a momentous occasion for the largest ever infrastructure project in our state’s history.

“After all the careful planning and machinery assembling, tunnelling is now underway to deliver South Australia a non-stop South Road.

“Once complete, the project will allow motorists to bypass 21 sets of traffic lights between the River Torrens and Darlington, saving up to 40 minutes of travel time in peak hour traffic.

“The scale of this project is extraordinary and I’m proud to be leading a government delivering such important infrastructure works for South Australia,” Premier Peter Malinauskas said.

TBM Mary will operate 24/7 and will progress about 8-10 metres per day, with around 20 specialised workers inside at any one time.

The first TBM component arrived in Adelaide in October 2025 and since then each component has been lifted into the launch box, piece by piece, with a 500-tonne gantry crane before being assembled into the massive machine now digging the tunnels for the non-stop South Road.

TBM Mary is one of the three large-scale machines being used on the T2D Project, measuring up to 100 metres in length, 15 metres in diameter and weighing 3,500 tonnes.

“Every day, thousands of South Australians have driven past the cranes, sheds and construction work reshaping South Road.

“Now, attention turns underground as the next chapter of the project begins, with tunnelling commencing on the non-stop South Road.

“This isn’t just the start of tunnelling; it’s the start of transforming how South Australians move about our city for generations to come,” SA Minister for Infrastructure and Transport Joe Szakacs said.

Project map (source: T2D Torrens to Darlington)

The project’s second TBM, Catherine, is going to be launched soon from the Southern Precinct to excavate the second parallel 4.5-kilometre Southern Tunnel.

TBM Elizabeth is the third to be launched from the project’s Central North Precinct at Hilton, and it will build the 2.2-kilometre Northern Tunnels.

The three TBMs are named after pioneering South Australian suffragists Mary Lee, Catherine Helen Spence and Elizabeth Webb Nicholls as recognition for the trailblazers who helped shape the State.

“This project is about giving commuter traffic a safer, faster route while leaving local roads for locals.

“It’s fantastic to see it really starting to take shape, and I look forward to the benefits it will unlock for our community,” Federal Member for Boothby Louise Miller-Frost said.

Operating three TBMs will allow both the Northern and Southern Tunnels to be built concurrently, enabling the delivery of a non-stop South Road by 2031.

An online tracker is available to follow TBM Mary’s journey, providing regular updates on approximate location as well as other key information. Updates on TBMs Catherine and Elizabeth will be available once they begin tunnelling.

The River Torrens to Darlington Project will deliver the final 10.5-kilometre section of the North-South Corridor, completing the 78-kilometre non-stop, traffic light-free motorway between Gawler and Old Noarlunga.

This massive transport infrastructure project is jointly funded by the Australian and South Australian Governments, each contributing $7.7 billion.

“The Albanese and Malinauskas Labor Governments are getting on with the job of delivering the infrastructure that will connect 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.

“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,” Federal Infrastructure, Transport, Regional Development and Local Government Minister Catherine King said.

The T2D Project is constructing two separate tunnels connected by an open motorway, with three lanes in each direction.

The overall project is comprised of:

• Southern Tunnels
  

  • Running between the open motorway at Darlington to just south of Anzac Highway in Glandore and provide key connectivity to Anzac Highway
  • Includes about 4 kilometres of twin three-lane tunnels
• Open motorway linking the tunnels
  • Connecting key routes such as Richmond Road and James Congdon Drive, it will provide critical east-west connectivity and links to key destinations such as the airport
  • Just over 2.5 kilometres in length
• Northern Tunnels
  • Running between James Congdon Drive and the existing open motorway south of Grange Road
  • Includes about 2.2 kilometres of twin three-lane tunnels

Source: Minister for Infrastructure, Transport, Regional Development and Local Government; T2D Torrens to Darlington (1, 2)