This $3.1b Sydney road has been delayed by years. Now there’s an ultimatum

The NSW government has issued the builders of a $3.1 billion underground motorway in Sydney’s south an ultimatum to resume work on the project by May 1 or face legal action, two years after it was halted by a sinkhole that opened up above one of the twin tunnels under construction.

The escalating dispute with a consortium led by CPB Contractors, which had been building the M6 motorway between Arncliffe and Kogarah, threatens to lengthen the three-year delay to the project’s completion.

Transport officials issued the contractors a default notice on Monday afternoon, telling them to resume tunnelling and other work by May 1 or face the prospect of legal action. They are considering hiring another contractor to finish the project if the consortium fails to resume construction.

NSW Motorways – a government agency set up last year – said the decision to issue a default notice was a “serious step” made only after extensive efforts to resolve the dispute, but that it was in the public interest to “limit further delay, uncertainty and risk”.

Chief executive Camilla Drover said the agency was “extremely disappointed” the project had not progressed, after it had engaged extensively with the contractors to work through technical challenges and options to restart the final 10 per cent of tunnelling.

“For more than two years, Transport has worked carefully, constructively and in good faith to try to resolve the issues affecting this project,” she said.

Work has been paused indefinitely on the final 244-metre section since March 2024, 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.

Transport officials say there is an engineering solution to complete the tunnels but the two sides have been in a stalemate for months over liability for the cost of the halt to construction and the fix.

Roads Minister Jenny Aitchison said the department had made clear there was a technical solution within the existing contract to finish the project, and that it was a reasonable community expectation that it was delivered.

“This is the right decision [to issue a default notice]. This is a major project paid for by the taxpayers of NSW, and the private contractor should take it seriously,” she said.

Aitchison will face intense questioning about the M6 dispute when she appears at a budget estimates hearing on Tuesday.

Earlier on Monday, Premier Chris Minns said the contractors would have to bear the cost under their design and construct contract for the M6.

“We can’t have a situation where in good faith the government lets out a contract, someone takes on the risk themselves, and then they get into difficulty, and they send the bill to NSW taxpayers,” he said.

In May last year, the contractors revealed they would stop all work indefinitely on the M6 because of the tunnelling conditions, before later agreeing to complete surface works.

Transport for NSW’s most recent target date for the M6’s completion is the end of 2028, which is three years later than a previously planned opening in late 2025. The latter was later than the original completion date of 2024. The timeline for the twin tunnels first slipped in 2021 by a year.

Budget papers from last June show the cost of the four-kilometre motorway is set to hit $3.193 billion, a $93 million increase on the most recent forecast.

CPB was approached for a response to the government’s ultimatum. Its consortium also comprises Ghella and UGL.

The M6, which will funnel motorists onto the WestConnex motorway at Arncliffe, will be tolled when it opens but it will remain in government hands under the Minns government’s policy.

The long-running saga over the M6 project comes as part of a highway over the Blue Mountains connecting Lithgow to Sydney has been shut indefinitely after cracks opened up in the road’s surface at Victoria Pass, near Mount Victoria.

The full closure of the Great Western Highway between Lithgow and Mount Victoria has forced detours to be put in place via the Darling Causeway and Bells Line of Road.

Transport for NSW said the discovery of cracks in the road at Mitchell’s Causeway, also known as the Convict Bridge, was an “evolving and complex situation”, and that it had no timeline for when the highway could be reopened.

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