Delivery of Torrens to Darlington Project continues to forge ahead

The Torrens to Darlington (T2D) Project in South Australia continues to forge ahead to deliver the missing link on the non-stop South Road with the establishment of a second purpose-built construction precinct. 

The Central North Construction Precinct is located in Richmond, between Sir Donald Bradman Drive and Keswick Creek. It will be the site where a third tunnel boring machine (TBM) is going to be assembled and launched to build the twin 2.2-kilometre tunnels. 

“The establishment of the Central North Construction Precinct is a significant milestone in creating a non-stop South Road that will ease congestion, improve safety and create more connected communities. 

“This is the second construction precinct to be established for the project and will be the site where one of the three main Tunnel Boring Machines will be assembled and launched to construct the 2.2-kilometre twin Northern Tunnels. 

“Every step forward on the River Torrens to Darlington Project brings South Australians closer to a more modern transport network that strengthen our state and serve our community for generations to come,” Deputy Premier Susan Close MP said. 

Bentonite plant silos at the Central North precinct (source: T2D - Torrens to Darlington)

Construction is underway at the Central North precinct to deliver the diaphragm walls that will form a deep, reinforced concrete pit called a ‘launch box’. The diaphragm walls will be up to 38 metres deep and built one panel at a time to form the launch box trench where the third TMB will be assembled and then commence excavating the twin tunnels. 

A bentonite plant has also been recently built at the precinct to produce and recycle bentonite slurry. The wet clay from the plant will be pumped into the trenches being excavated for the diaphragm walls to ensure ground stability. 

Nine 14-metre-tall silos have been installed in the bentonite plant, which can hold 90 cubic metres of bentonite slurry each. 

In addition, a water treatment plant is being built to treat and reuse water during the tunnelling process alongside a 100 cubic metre buffer pond to hold spare water produced by construction activities. 

More than 500 workers are estimated to be employed to work at the Central North Construction Precinct during peak construction. 

“It’s great to see this latest stage of site preparations proceeding at pace. 

“Boothby residents who regularly travel South Road know what a parking lot it can be, day and night. We are very much looking forward to the tunnels taking commuter traffic off South Road and speeding up our journeys,” Federal Member for Boothby Louise Miller-Frost said. 

Meanwhile at the Southern Precinct at Clovelly Park, works are already underway to enable the first two TBMs to be launched from the site to construct the 4.5-kilometre Southern Tunnels that will run between the open motorway at Darlington to just south of Anzac Highway in Glandore. 

The entire Torrens to Darlington Project is anticipated to support approximately 5,500 jobs annually during the main construction stage, with about 90 per cent of labour hours to be undertaken by South Australians – creating a skills legacy for the State. 

Components of the TBMs are being manufactured in Germany and China, and will be assembled and factory assurance tested in China before shipping to Adelaide. The first three TBMs are due to arrive later this year. 

Excavation of the Southern Tunnels is scheduled to begin in the second half of 2026. 

Project map (source: T2D - Torrens to Darlington Project)

The $15.4 billion Torrens to Darlington Project will deliver the remaining 10.5-kilometre section of the South Road, completing the non-stop, traffic light-free motorway between Gawler and Old Noarlunga. 

The project is comprised of: 

• Southern Tunnels 

• • Run 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 

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

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

“When I talk to my community about this project the most common comment is: ‘Let’s get it done’. 

“And that’s exactly what this Government is doing. Work is on time and on budget and locals are glad to see progress well underway. 

“We’ve been waiting a long time to see this happen and I’m thrilled our Government is getting on with it,” State Member for Badcoe Jayne Stinson said. 

Source: Government of South Australia – Media Releases; T2D – Torrens to Darlington (1, 2); Infrastructure Magazine