Construction has officially begun on South Australia’s largest-ever infrastructure project, with major works now underway at the Southern Precinct of the $15.4 billion Torrens to Darlington (T2D) tunnel section of South Road.

The Clovelly Park site, positioned between Tonsley Boulevard and Norrie Avenue, will serve as the launch point for two 4.5km tunnel boring machines (TBMs) that will excavate the southern tunnels. These twin tunnels are part of the final missing link in Adelaide’s 78km North-South Corridor.

Crews have commenced construction of 35-metre-deep diaphragm walls that will form the permanent TBM launch box. The trench will house three large piling rigs and a 500-tonne gantry crane to handle TBM assembly. A spoil handling facility and a closed conveyor system will manage tunnel excavation waste.

A bentonite plant, nearly 100 metres in length, is operational on site to support trench stability during wall construction. A water treatment facility has also been installed to enable slurry recycling and reduce demand on potable water.

Three Herrenknecht TBMs – procured in late 2024 – will drive the 4.5km southern and 2.2km northern twin tunnels. The first machine is expected to arrive in Adelaide by late 2025, with tunnelling due to begin in the second half of 2026. Two smaller TBMs will excavate cross passages between the main tunnels.

The T2D Alliance estimates the Southern Precinct will host up to 550 workers during peak construction, with broader project employment expected to support 5,500 jobs annually. Workforce commitments include 90 per cent South Australian labour, a 6 per cent Aboriginal employment target, and over 600 roles for apprentices and trainees.

Early works completed in 2023 included the Tonsley East Substation and new access roads. Local contractor McMahon Services recently delivered a $6 million link road connecting Norrie Avenue to English Avenue, allowing for the closure of Celtic Avenue during TBM launch area construction.

The full T2D project is jointly funded by the Federal and South Australian Governments, each contributing $7.7 billion. The corridor is scheduled for completion by 2031.