Major construction work has begun this month on South Australia’s largest and most complex infrastructure project to date – the $15.4 billion River Torrens to Darlington (T2D) Project, which will create a non-stop South Road.
The project has been jointly funded by the state and federal governments, with each contributing $7.7 billion.
The non-stop South Road project will allow motorists to bypass 21 sets of traffic lights between the River Torrens and Darlington, expected to save up to 40 minutes of travel time in peak hour traffic.
Minister for Infrastructure, Transport, Regional Development and Local Government Catherine King, said, “This is the last leg of a long journey to create the North-South Corridor – 78km of non-stop, traffic light-free motorway – and once complete, it will change the state for the better.”
SA Minister for Infrastructure and Transport Tom Koutsantonis added, “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.”
The Southern Precinct – located between Tonsley Boulevard and Norrie Avenue on the western side of South Road – will become the purpose-built site from where the Tunnel Boring Machines (TBMs) will launch to construct the southern tunnels.
Two TBMs will launch from the Southern Precinct to construct the twin 4.5km Southern Tunnels, while the twin 2.2km Northern Tunnels will utilise a third TBM. TBM works for the Southern Tunnels are planned to begin in the second half of 2026.
Recent weeks have seen the start of construction of the diaphragm walls for the TBM launch box – the first piece of permanent works on the project.
The diaphragm walls will be up to 35m deep and form the outside of the TBM launch box – a large open trench where the TBMs will be assembled and then begin excavating the tunnels.
A nearly 100m-long bentonite plant has also been constructed. This will produce and recycle bentonite slurry – a wet clay that is pumped into the trenches being excavated for the diaphragm walls to ensure ground stability. A water treatment plant, which will help the project treat and reuse water during the tunnelling process, has also been constructed.
The Southern Precinct site’s Tonsley East Substation – built on the precinct in 2023 – will supply electricity to the TBMs and then to the Southern Tunnels once they are completed.
A link road between Selgar Avenue and MAB Circuit in Tonsley was constructed in 2023 on the western side of the precinct, one of numerous upgrades to surrounding streets to maintain local connectivity.
This includes a $6 million link road between Norrie Avenue and English Avenue, Clovelly Park, which opened to traffic on Sunday, May 11.
These works will enable the planned temporary closure of Celtic Avenue, which is necessary for the construction of the Southern Tunnel portal and the TBM launch area. The new signalised intersection will maintain connectivity to and from South Road for the local community during this closure.
“This is a project that’s been long talked about – everyone knows how important it is. Now we’re getting on with delivering it,” said South Australia Premier Peter Malinauskas.
“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 construct the 4.5km Southern Tunnels, which will run from Clovelly Park to just south of the Glenelg Tramline in Glandore.
“This massive precinct, which is approximately 1300 metres 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.”
The three TBMs were purchased in September 2024 from German manufacturer Herrenknecht.
The TBM components are being manufactured in Germany and China, before being assembled and factory assurance tested in China, and then delivered to Adelaide by ship. The first of three TBMs is expected to arrive in late 2025.
Two additional, smaller TBMs will also be used to carry out excavation work for cross passages between the main tunnels.