Contractors face a daunting task revising work on a 244-metre stretch of road tunnels and shifting a major gas line to complete a new motorway in Sydney’s south, which the NSW government has confirmed will be delayed by years.
Following a report by the Herald about the extent of delays, Roads Minister John Graham confirmed that early indications from contractors were that “there may be years’ delay” to finish the first stage of the M6 toll road due to the difficult conditions caused by two sinkholes in March.
“This work is so difficult there may be very significant delays,” he said.
Workers fill in the huge sinkhole with cement in March to stabilise a two-storey building that teetered on the edge.Credit: Rhett Wyman
The first stage of the M6 comprises four-kilometre twin tunnels between President Avenue at Kogarah and the WestConnex motorway at Arncliffe.
The long delays to the first stage also cast further doubt on future stages of the M6, which would extend the toll road to Loftus near the Royal National Park.
Neither the previous Coalition government nor its successor committed funding to stages two or three, and Graham said the priority was to finish “what is a very difficult tunnelling work” on the first stage.
The first sinkhole opened on March 1 above one of the tunnels at Rockdale for the M6 motorway.Credit: Fire and Rescue NSW
Work has been paused indefinitely on a 244-metre section of the first stage since March 1, when a 10-metre-wide sinkhole suddenly opened up above one of the twin tunnels at Rockdale. Days later, another emerged about 150 metres away in a construction area on the eastern side of West Botany Street.
Graham said the delays caused by the sinkholes would have implications for the cost of the project, which blew out by $500 million to $3.1 billion in 2022. But he said the government would not accept that the taxpayer would be on the hook for a bigger bill.
The 244-metre section at Rockdale where the sinkholes opened up is now the subject of technical studies to work out how the motorway can be finished.
Transport for NSW infrastructure deputy secretary Camilla Drover said it could be “many years” before the project was completed, and advice from the contractor was that it was “definitely more than 24 months”.
“Whether it’s up to three years or longer, we’re still working through that,” she said.
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.
Drover said it was likely that additional utilities would have to be relocated, potentially including a major gas line, high-voltage cables and water mains. “There will also be ground stabilising works ahead of that,” she said.
Asked whether there would be any impact on nearby houses during the relocation of utilities, Drover said there might be some disruption to West Botany Street but at this stage the transport agency was not anticipating any impact on residential properties.
She said there would be extra costs from the project’s delay and the extra work to complete the 244-metre stretch of tunnels, but she declined to put a figure on the quantum of the blowout.
“That is subject to very complicated insurance and commercial processes,” she said. “Insurance is quite complicated – it goes to causation.”
Transport for NSW contracted a joint venture among contractors CPB, UGL and Ghella to build the motorway.
The agency has yet to complete its investigation into the exact cause of the sinkholes, although Drover noted that it was “soft ground conditions” in the area where they opened up and the tunnelling had been at a shallow depth.
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