The 10.5km long River Torrens to Darlington Project (T2D Project) North-South Corridor has reached a major milestone, with a preferred alliance partner being selected for the project. Following an exhaustive procurement process which commenced in January 2023, the consortium, comprising John Holland, Bouygues Construction, Arcadis Australia, Jacobs and Ventia, has been selected as the preferred alliance partner to deliver South Australia’s biggest-ever infrastructure project.
The T2D Project involves the construction of two separate tunnels – the Southern Tunnels and the Northern Tunnels – that will be connected by an open motorway. The motorway and the tunnels will all have three lanes operating in each direction, with a combined total distance of 10.5km.
Southern Tunnels
- Run between the open motorway at Darlington to just south of Anzac Highway in Glandore and provide key connectivity to Anzac Highway
- Includes about 4km of twin three-lane tunnels
Open motorway linking the tunnels
- Connecting to key routes such as Richmond Road and James Congdon Drive, it will provide critical east-west connectivity and links to key destinations such as the airport
- Just over 2.5km in length
Northern Tunnels
- Run between James Congdon Drive and the existing open motorway south of Grange Road
- Includes about 2.2km of twin three-lane tunnels
When complete, more than 50% of the T2D Project will be tunnels.
The consortium’s tender detailed a plan to procure three TBMs instead of the two previously anticipated – which will mean both north and south tunnels can be constructed concurrently.
Once finished, the T2D project will allow motorists to avoid 21 existing sets of traffic lights between the River Torrens and Darlington and will complete the non-stop 78km North-South Corridor between Gawler and Old Noarlunga.
The three TBMs that will be used to excavate the T2D tunnels will be purpose-built for the local conditions they will encounter on this project.
The additional TBM gives the project a reasonable expectation that it can not only be completed by the stated 2031 deadline – but even earlier.
The successful consortium’s design delivers the key features of the December 2022 Reference Design release, while providing further traffic and community benefits.
Enhancements from the 2022 Reference Design proposed by the successful consortium include:
- A connection free from traffic lights between the motorway and James Congdon Drive, providing seamless access to and from the CBD;
- Innovative tunnel portal arrangements that enable improved and lowered motorway sections with faster construction times and reduced costs;
- More trees planted to help green the corridor;
- Improved tunnel design and shorter cut and cover tunnel sections, which will reduce energy use and costs, and minimise surface impacts to communities next to the T2D motorway;
- Innovation for the construction of tunnel cross passages, and other systems elements of the tunnels; and
- Improved experience for active travel users with universally accessible paths, shared-use paths and active travel corridors, with regular safe east-west connections.
In the coming weeks, the construction consortium will set up the major construction site at the southern laydown area in Clovelly Park and engaging with local communities as early works continue along the corridor.
Main construction works are proposed to start in 2025, with tunnel boring machine works for the southern tunnels planned to begin in the second half of 2026.
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