The location of the sinkhole near the M6 site in Rockdale.Credit:Google Maps
The under-construction M6 southbound tunnel is about 18 metres below where the sinkhole is.
Ackerman said the collapse was a reminder of the “very dangerous” work involved in tunnelling,citing the long delays to theSnowy 2.0 pumped hydro project after a massive boring machine got stuck in soft rock beneath Kosciuszko National Park.
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“There is a certain inherent risk and unpredictability about working underground,” he said.
The cost of the M6 motorway tunnels blew out byabout $400 million to more than $3 billion in 2022. The first stage of the toll road,which will link Kogarah to the WestConnex motorway at Arncliffe,is due to be opened to traffic by the end of 2025,about a year later than originally planned.
The cost of the latest cleanup at Rockdale will rest with the M6 contractor,which is a joint venture between CPB Contractors,UGL and Ghella.
Executive project director Terry Sleiman said it was too early to determine the cause of the sinkhole,or the cost to repair the damage.
“There was nothing leading up to[the sinkhole appearing] that would have suggested there were any issues,” he said. “There are a lot of factors,obviously,when we’re tunnelling. There’s water,varying geology and the like,so that’ll all be borne out in the investigation.”
Building engineers and Fire and Rescue NSW have been using laser technology to monitor any further movement in the building as they work to determine the extent of the structural faults.
NSW Fire and Rescue set up an exclusion zone around the building in Rockdale.Credit:Dominic Lorrimer
Fire and Rescue NSW Superintendent Peter Cleary said the 10-metre-wide hole extended under the office building.
“It does go under the building,and it goes under a concrete slab. That’s why we have a large exclusion zone in place around it. We haven’t seen any further expanding of the hole,” he said.
Rockdale resident Janet Lam,whose house is near the M6 tunnels,said she was shocked to hear about the sinkhole. “There is a lot of construction going on,and this was unexpected,” she said.