Nearly two years after sinkholes opened, fix for halted Sydney motorway remains unresolved

2 months ago 18

Almost two years after a large sinkhole halted construction of a $3.1 billion motorway in Sydney’s south, the NSW government remains locked in negotiations with contractors and unable to say what the engineering fix will be.

The cost of finishing the first stage of the M6 motorway between Arncliffe and Kogarah will hinge on the revised design of a 244-metre stretch of tunnels, and complex talks over liability for the three-year delay to the project’s opening.

The first sinkhole opened above one of the tunnels at Rockdale for the M6 motorway in early March 2024.

Transport for NSW secretary Josh Murray said the project remained a “very complex technical and commercial issue” for the department.

Work has been paused indefinitely on the 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.

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.

Asked about the likely engineering solution, Murray said the department and contractors had brought in extra assistance to get the “best possible response”, adding that it was on the proviso that it was value for money for taxpayers.

“We’re not in a position to talk about any of the feasible technical responses … at this stage, except to say that we’ve asked for every idea to be brought forward that delivers the best result,” he said.

“What we want to see is the engineers put their best work forward that we can review and take that back to government.”

Murray said the latest cost estimate for completing the motorway would be determined by the revised design and construction time frame.

“We don’t have that final picture yet, but we are getting close,” he said.

CPB Contractors leads the consortium building the motorway project, which also comprises Ghella and UGL.

Workers fill in a large sinkhole with cement in March 2024 to stabilise a two-storey building that had teetered on the edge.

“[The consortium] have a design and construct contract that they need to deliver on. We also need to take into account what that impact is on taxpayers and motorists,” Murray said.

“When we have all of those pieces together, we’ll be able to provide a full update on what that means in terms of timing and its inclusion with the rest of the network.”

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

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

The government will introduce charges for northbound trips on the Sydney Harbour Bridge and Harbour Tunnel from as early as 2028, which will be used to help pay for a permanent extension of a $60-a-week cap on tolls across the city. The cap had been due to expire on New Year’s Day.

A government-commissioned review led by former competition watchdog chairman Allan Fels also called for two-way tolling on the Eastern Distributor motorway.

Asked whether two-way tolling would be applied to the Eastern Distributor, Transport Minister John Graham said no decisions about other Sydney motorways had been made, which were the subject of long-running negotiations with toll operator Transurban about a shake-up of the tolling system.

“We’re not confirming arrangements for any of the other roads as those tough discussions go on,” he said on Thursday.

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