This section of works will transform the 10.5 kilometre stretch of road between River Torrens to Darlington over the next decade. Design of the upgrade will include a combination of tunnels and surface level motorway.
Due to the location of the final section, it is the most complex to design and deliver as it is situated close to unique heritage assets.
Minister for Infrastructure and Transport, Corey Wingard, said the locations selected for the ground investigation and engineering survey works do not necessarily correspond to areas that will be impacted by the project in the final design.
“Ground investigation works commenced with one drill rig in August this year, and have progressed to four concurrently operating rigs now in action,” Wingard said.
“A fifth rig is due to commence in the coming weeks and Phase Two of these works are due to commence in March 2021.”
Boreholes of approximately 10 centimetres in diameter, at depths of between 30 to 100 metres, have been drilled at 36 locations. The total depth drilled equates to more than 1.4 kilometres.
By the end of January 2021, nearly 5,000 tests are expected to have been carried out across 200 testing locations.
The samples from these tests will be examined in local laboratories. Results will help to determine the depth and route the tunnels may take.
The completion of the River Torrens to Darlington section will deliver a 78km non-stop, free-flowing motorway that seamlessly links Gawler, to the north of the city, with Old Noarlunga in the south.