A $3.1 billion underground motorway in southern Sydney is at risk of opening three years late due to a giant sinkhole forcing a redesign of the tunnels and much slower excavation when tunnelling eventually resumes.
Two sources close to the project, who spoke on the condition of anonymity due to the sensitivity of the matter, said completion of the new M6 toll road tunnels was likely to be delayed until 2027 and could be as late as 2028.
The motorway had previously been scheduled to open to motorists by the end of 2025, which was already later than the original completion date of this year. The timeline for the twin tunnels first slipped in 2021 by a year.
The first stage of the new M6 motorway is facing major delays.Credit: Janie Barrett
Work has been paused indefinitely on a 244-metre section of the first stage of the M6 since March 1, when a 10-metre-wide sinkhole suddenly opened up above one of the twin tunnels at Rockdale, leaving a two-storey building at risk of collapse and forcing workers to evacuate.
Just over a week after the major sinkhole in March, another emerged about 150 metres away in a fenced-off construction area on the eastern side of West Botany Street.
Transport for NSW said in a statement that it was carrying out a detailed analysis of the time and cost impacts from the “two subsidence incidents” and was working closely with contractors to finalise a tunnelling program in the affected areas.
The sinkhole opened on March 1 above one of the tunnels at Rockdale for the M6 motorway.Credit: Fire and Rescue NSW
The agency said SafeWork would have to be satisfied before tunnelling work resumed.
A senior transport official told a budget estimates hearing last month that, due to the complexity of the process, she did not expect tunnelling to resume until the second half of 2025.
The implications of the delays and tunnel redesign on the project’s cost are the subject of complicated legal, commercial and insurance processes.
Coalition roads spokesperson Natalie Ward said the state government needed to be upfront with the public on the status of the M6 project and potential cost implications of the ongoing delays.
Transport for NSW had previously confirmed that the redesign and changed construction program would “impact the cost of the project” but has not elaborated on the expected size of the blowout or the length of the delay to the motorway’s opening.
The first stage of the M6 comprises twin three-lane tunnels between President Avenue at Kogarah and the WestConnex motorway at Arncliffe.
Transport for NSW contracted a joint venture among contractors CPB, UGL and Ghella to build the motorway, the cost of which blew out by $500 million to $3.1 billion in 2022.
While construction on the Rockdale section has stopped, work on the rest of the motorway, including tunnel lining and electrical fit-outs, is continuing. Transport for NSW said most road surface works would be completed by the middle of next year.
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