Contractors will finally return to work on the final section of a $3.2 billion motorway in Sydney’s south after reaching a deal with the NSW government to complete tunnels damaged by sinkholes more than two years ago.
In a bid to end their protracted dispute, the two sides have agreed to leave resolution of any claims arising from the long-delayed project until after the M6 motorway is completed, which is not expected to happen until 2029. That is more than four years later than the original completion date of 2024.
Construction was halted on the final 244 metres of the four-kilometre underground motorway in March 2024 after a sinkhole opened 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.
Contractors plan to use an engineering technique known as jet grouting to complete tunnelling near where the sinkholes opened up. The technique is favoured in soft ground conditions like those at Rockdale and involves using high-pressure fluid jets to erode soil and mix it with cement.
As part of the deal, the government said the consortium led by CPB Contractors which is building the motorway had agreed not to pursue contractual claims against the government for costs relating to the two sinkholes in 2024.
Roads Minister Jenny Aitchison said the agreement meant construction would resume immediately under the original contract, and at “no additional cost” to the government.
“Our priority has always been to complete this project under the existing contract. With 90 per cent of tunnelling already complete, we now have a clear path to finishing the job,” she said.
So far, the government has shelled out at least $2.7 billion on the motorway, which has been budgeted to cost the state $3.2 billion.
CPB executive project director Terry Sleiman confirmed an agreement had been reached with Transport for NSW, welcoming the “opportunity to continue tunnelling works” on the project.
The government had been at loggerheads with the CPB-led consortium for the past two years over who bears the major cost of fixing tunnels damaged by the sinkholes.
In March, Transport for NSW attempted to bring the dispute to a head by issuing the consortium an ultimatum to resume work by May 1 or face legal action.
The agency later rejected an offer by the contractors to complete the motorway, deeming it inadequate but giving them more time to return to the table with an improved one.
Transport for NSW secretary Josh Murray said the agency had negotiated “fairly and in good faith” with the consortium.
“While there has been a regrettable delay, the contract for the M6 stage one has clear dispute resolution processes and these will be used – ending the threat of walk-offs and the need for termination – with a deed putting the interests of taxpayers, motorists and residents first,” he said.
The government has said that the M6 will not be completed by the end of 2028, which had been its most recent target date. That is three years later than a previously planned opening in late 2025.
However, the original completion date under the former Coalition government was 2024.
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Matt O’Sullivan is transport and infrastructure editor at The Sydney Morning Herald.Connect via X or email.
