SA Torrens to Darlington Project sees changes in design

Several changes have been made to the final section of South Australia’s North-South Corridor after the State Government undertook a comprehensive design and financial review on the River Torrens to Darlington (T2D) project. 

The approximately $15.4 billion project will now include the removal of large, elevated roadways as well as adding new entry and exit ramps. 

The 10.5-kilometre T2D section of the North-South Corridor will consist of two sets of twin tunnels, lowered and ground-level motorways along with overpasses and underpasses at key intersections. 

Key changes proposed for the project include: 

• Torrensville area – at the northern portal of the Northern Tunnels, near where the T2D Project connects to the North-South Motorway, a proposed large elevated roadway running parallel to the Brickworks Marketplace has been removed, with the motorway corridor moving to the east. Instead, a shorter, low-height structure over the corner of the Hindmarsh Cemetery will be constructed. This improvement, along with changes to the construction methodology, means the project will require less of Kings Reserve during construction than previously planned. 
• James Congdon Drive / Deacon Avenue – an additional exit ramp for vehicles travelling north has been added near this intersection, providing access to Richmond Road and James Congdon Drive. This means vehicles travelling from the south, heading north to go to Adelaide Airport or the western suburbs, do not need to go through the Anzac Highway intersection, greatly reducing the number of vehicles on the surface road there and increasing travel options for motorists. An additional entry ramp at James Congdon Drive has also been provided for traffic wanting to enter the motorway and head south. 
• Anzac Highway connection – the elevated ramp going over the motorway and South Road, before coming down onto the middle of Anzac Highway at Ashford to join with citybound traffic, has been scrapped. Instead, three ground-level right-turn lanes onto Anzac Highway heading towards the city will be provided, with an additional exit ramp from the River Torrens to Darlington motorway for northbound traffic, north of the Anzac Highway intersection. Right turns from Anzac Highway onto South Road – which were removed in the 2021 Reference Design – have been reinstated, acknowledging strong community feedback. This solution reduces traffic at Anzac Highway intersection and the number of trees needing to be removed (approximately 35 instead of 116). 
• Darlington connection – the southern portal of the Southern Tunnels will shift about 300 metres to the north to give traffic more distance and time to safely change lanes, while moving into and out of the new motorway. This provides the opportunity for better cross-corridor movement via a shared-use bridge, significantly reduces the duration of required closures of the Darlington motorway during construction (easing disruption for motorists) and reduces the length of the Southern Tunnels and the associated construction costs. 

A revised delivery program was also recommended following the project review, which will get construction of the Southern and Northern Tunnels delivered sequentially rather than overlapping. This delivery program is a more realistic approach to project timing and market capacity. 

Some properties earmarked for acquisition before the review and revision of plans will no longer be required, but the updated designs will result in a net increase of 112 properties required to build the T2D project. 

Early works are already underway and main construction will begin in 2025, with the tunnel boring machine in the ground working on the Southern Tunnel in 2026. 

A series of community information sessions is going to be held in early 2023 along the project alignment where the project team will engage with interested stakeholders to gain local insights that will further inform the project's design.

The procurement process for T2D is also anticipated to commence in early 2023, with the contract to deliver the project awarded in 2024.

The River Torrens to Darlington Project is due to be completed in 2031 and it will complete the 78-kilometre non-stop motorway between Gawler and Old Noarlunga as well as allow motorists to avoid 21 sets of traffic lights between the River Torrens and Darlington. 

Source: SA Department of Infrastructure and Transport – Torren to Darlington (1, 2); ABC News; Infrastructure Magazine