Main construction work on $15.4bn Torrens to Darlington Project begins

Main construction activities have officially commenced on South Australia’s largest and most complex infrastructure project – the $15.4 billion River Torrens to Darlington (T2D) Project. 

With heavy machinery now on site at the Southern Precinct in Clovelly Park, construction works will ramp up to deliver the final 10.5-kilometre section of the North-South Corridor. 

The T2D Project will complete the 78-kilometre non-stop, traffic light-free motorway between Gawler and Old Noarlunga. Once completed, motorists will be able to bypass 21 sets of traffic lights while travelling through two separate tunnels that are connected by an open motorway. 

This multi-billion-dollar development is jointly funded by the Australian and South Australian Governments, each contributing $7.7 billion. 

“The start of major works on South Australia’s biggest ever road project is a significant milestone for the state. 

“This is the last leg of a long journey to create the North-South Corridor – 78 kilometres of non-stop, traffic light-free motorway – and once complete, it will change the state for the better. 

“When South Australians can bypass 21 sets of traffic lights on their journeys between River Torrens and Darlington, they won’t know themselves,” Minister for Infrastructure, Transport, Regional Development and Local Government Catherine King said. 

“This is another demonstration that the Australian and South Australian governments are investing in the infrastructure Adelaide needs to keep up with growing demand. 

“Once completed, the T2D Project won’t just benefit locals in my electorate and beyond, but also the millions of tourists who visit the area each year,” Federal Member for Boothby Louise Miller-Frost said. 

The entire T2D Project is estimated to support 5,500 jobs annually during the main construction phase, with about 90 per cent of labour hours to be undertaken by South Australians. The Southern Precinct is expected to see up to 550 workers on site at peak construction period. 

The River Torrens to Darlington Project has three construction precincts – Southern, Central and Northern – and each precinct will accommodate tunnelling works as well as surface level construction activities to deliver the lowered motorway and associated urban infrastructure. 

The Southern Precinct – where works are currently progressing – is located between Tonsley Boulevard and Norrie Avenue on the western side of South Road. This precinct will become a purpose-built site where tunnel boring machines (TBMs) will be launched to construct the southern tunnels. 

Two TBMs will launch from the Southern Precinct to build the twin 4.5-kilometre Southern Tunnels – planned to start in the second half of 2026. Meanwhile, the 2.2-kilometre Northern Tunnels will utilise a third TBM. 

A significant increase in works were seen on site over the past few weeks. This includes the beginning of construction of the diaphragm walls for the TBM launch box, which is the first piece of permanent works on the project. 

The diaphragm walls will be about 35 metres deep, forming the outside of the TBM launch box – an open trench where the massive diggers will be assembled and then begin excavating the tunnels. 

In addition, a nearly 100-metre-long bentonite plant and a water treatment plant have also been constructed. The bentonite plant will produce and recycle bentonite slurry; a wet clay pumped into the trenches being excavated for the diaphragm walls to ensure ground stability. The water treatment plant, on the other hand, will help the project treat and reuse water during the tunnelling process. 

The Tonsley East Substation was built on the Southern Precinct in 2023, and this will supply electricity to the TBMs and to the Southern Tunnels once they are completed. 

A link road between Selgar Avenue and MAB Circuit in Tonsley was also constructed in 2023 on the western side of the precinct. This is one of several upgrades to surrounding street to maintain local connectivity. 

“Today is such an important day for our state with the start of major construction to create a non-stop South Road. 

“This is a project that’s been long talked about – everyone knows how important it is. Now we’re getting on with delivering it! 

“Residents in the Tonsley and Clovelly Park areas will be seeing works underway at the Southern Precinct between Tonsley Boulevard and Norrie Avenue. 

“The purpose-built site is where the Tunnel Boring Machines will launch to contruct the 4.5 kilometre Southern Tunnels, which will run from Clovelly Park to just south of the Glenelg Tramline in Glandore. 

“This massive precinct, which is approximately 1,300 metre long and 100 metres wide, will feature three large rigs and associated cranes to build the retaining walls, a 500-tonne gantry crane initially to lift and place the TBM components, multiple storage sheds including a large spoil handling facility and a large enclosed conveyor system to shift ground material from the tunnels to the spoil handling shed. 

“SA is building – and we are now building a non-stop South Road that will leave a legacy for generations,” Premier Peter Malinauskas said. 

“The Southern Precinct is really taking shape, and I’m so grateful to residents around the site for their incredible patience as the Government delivers this incredibly significant project. 

“The completion of the new link road between Norrie Avenue and English Avenue in Clovelly Park will be a huge help for local motorists during other necessary closures,” State Member for Elder Nadia Clancy said. 

Project map (source: T2D Torrens to Darlington)

The preferred delivery partner for the T2D Project was announced last year. The consortium is comprised of John Holland, Bouygues Construction, Arcadis Australia, Jacobs and Ventia. 

The T2D Project is anticipated to leave a skills legacy for the State, with the project alliance committing to a minimum of 6 per cent Aboriginal employment alongside more than 600 jobs for apprentices and trainees, and opportunities for over 220 long-term unemployed people. 

The Alliance awarded its first package of works – a $6 million contract – to deliver a link road between Norrie Avenue and English Avenue, Clovelly Park. Local contractor McMahon Services carried out the works and the new link road is now open to traffic. 

These works will allow Celtic Avenue to temporarily close. This is a necessary step in the construction of the Southern Tunnel portal and the TBM launch area. A new signalised intersection will maintain connectivity to and from South Road for the local community during the road closure. 

The three TBMs to be used in the excavation of the T2D tunnels were purchased in September 2024 from world-leading manufacturer Herrenknecht based in Schwanau, Germany. 

Components of the TBMs are being manufactured both in Germany and China before they are assembled and factory tested in China. The parts will then be delivered to Adelaide by ship. The first TBM is expected to arrive in late 2025. 

The project will also utilise two smaller TBMs to dig the cross passages between the main tunnels. 

The T2D Alliance team will regularly engage with the community, including at information sessions held along the alignment, to share updates as well as answer questions about the project. 

“We’ve wasted no time in getting on with the largest infrastructure project in South Australian history. 

“The T2D Alliance has awarded its first package of works, with local company McMahon Services already delivering an important link road between Norrie Avenue and English Avenue in Clovelly Park, which will help maintain access to and from South Road during T2D main construction. 

“We have full confidence this State-shaping project will be open to traffic as promised by 2031, if not even earlier, providing South Australians with a range of transport, safety, economic and social benefits,” SA Minister for Infrastructure and Transport Tom Koutsantonis said. 

The River Torrens to Darlington Project is made up of the following: 

• Southern Tunnels 

• • Running between the open motorway at Darlington to just south of Anzac Highway in Glandore and provide key connectivity to Anzac Highway 

• • Include 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 

• • Will be just over 2.5 kilometres in length 

• Northern Tunnels 

• • Run between James Congdon Drive and the existing open motorway south of Grange Road 

• • Includes about 2.2 kilometres of twin three-lane tunnels 

The entire T2D Project is expected to be completed and opened to traffic in 2031. 

“This is a significant project that, once completed, will create four kilometres of twin three-lane tunnels to the south and 2.2 kilometres to the north, connected by open motorway. 

“This project, which is jointly funded by the Australian and South Australian Governments, will bring much relief to travellers by saving time in traffic, and it allows South Australia to keep up with the demands on the state. 

“I’d like to thank the community for their patience while we deliver this transformative infrastructure project,” Federal Member for Adelaide Steve Georganas said. 

“My community knows how important a non-stop South Road will be for South Australia, and just wants to see this project underway. 

“It’s fantastic to see major works kick off, and construction really ramping up before the tunnelling work kicks off,” State Member for Badcoe Jayne Stinson said. 

Source: Government of South Australia – Media Releases; T2D Torrens to Darlington (1, 2, 3); Government of South Australia – Department for Infrastructure and Transport; Minister for Infrastructure, Transport, Regional Development and Local Government; Roads & Infrastructure Australia