South Australia Sets Milestone on $15.4 Billion T2D Project as Three Tunnel Boring Machines Operate Simultaneously for First Time in Australian History

Historic Civil Engineering Feat Beneath Metropolitan Adelaide

ADELAIDE, South Australia — Achieving an unprecedented civil engineering milestone in Australian transport history, the South Australian Government and the T2D Alliance have confirmed that all three gigantic Tunnel Boring Machines (TBMs) are now actively excavating beneath metropolitan Adelaide on the landmark $15.4 billion River Torrens to Darlington (T2D) Project. This marks the first time in Australian history that three mega-scale TBMs have operated concurrently on the same subterranean roadway infrastructure project.

The multidisciplinary T2D Alliance—comprising John Holland, Bouygues Construction, Arcadis Australia, Jacobs, and Ventia—is delivering the 10.5-kilometre motorway project, which forms the definitive final link in completing Adelaide’s 78-kilometre continuous, non-stop North-South Corridor between Gawler in the north and Old Noarlunga in the south.

Synchronized Excavation Across Northern and Southern Twin Tunnels

The subterranean operations deploy two specialized machine configurations tailored to Adelaide’s distinct geological strata. In the Southern Precinct at Clovelly Park, twin TBMs named 'Mary' and 'Catherine' are methodically excavating the 4.5-kilometre Southern Tunnels toward Glandore, carving deep passageways beneath South Road with custom 15-metre-diameter rotating cutterheads.

Concurrently, in the Central North Precinct at Hilton, a third massive machine, named 'Elizabeth', has launched subterranean tunneling for the 2.2-kilometre Northern Tunnels toward Richmond. The twin tunnel systems will be seamlessly interconnected by a 2.7-kilometre open lowered motorway section, completely bypassing 21 sets of surface traffic lights and slashing peak-hour journey times for Adelaide motorists by up to 40 minutes.

Local Advanced Manufacturing Powers Precision Precast Tunnel Segments

Powering the relentless pace of excavation is South Australia's state-of-the-art precast concrete manufacturing facility at Waterloo Corner. Employing hundreds of local specialized fabricators, technicians, and concrete engineers, the high-tech plant is manufacturing tens of thousands of precision-cured, steel-reinforced tunnel lining segments.

As each TBM advances, its mechanized erector arm locks these curved interlocking segments into place with millimetre precision, creating an impenetrable, waterproof structural ring capable of supporting Adelaide's high-volume freight corridor for over a century.

Unlocking Freight Productivity and Reclaiming Urban Liveability

State infrastructure ministers emphasized that the T2D project is a transformative catalyst for South Australia’s economic productivity and environmental quality. By diverting heavy multi-trailer freight and intermodal shipping transport away from residential arterial streets into subterranean expressways, the project drastically reduces neighborhood noise pollution and stop-and-go vehicle emissions.

At surface level, the decommissioned corridor spaces will be transformed into lush community parklands, tree-lined civic boulevards, and protected off-road cycling highways, elevating urban liveability across Adelaide's inner-western and southern suburbs well toward its targeted 2031 delivery date.