No connection between two sinkholes over troubled M6 project: contractor

There is no connection between two sinkholes which opened up above the embattled M6 Tunnel project, a contractor says.

A contractor responsible for the embattled M6 tunnel project has explained there is any connection between two sinkholes which have opened up above the project in just over a week.

Workers were around 12 metres below the surface on Saturday morning when they evacuated from the tunnel after noticing a “slight movement” in the roof.

Sandy clay began leaking into the tunnel, which is now closed for remediation and investigation.

The subsidence has caused a visible sinkhole on the surface at a site on the airport side of West Botany Street in Rockdale.

The site is around 150m away from another area of the tunnel, which was evacuated on March 1 when a large sinkhole appeared and caused a partial building collapse.

A second sinkhole opened up above the troubled M6 Tunnel project on Saturday. Picture: Transport for NSW

The subsidence occurred within the construction site. Picture: Transport for NSW

On Sunday, CPB Contractors tunnelling general manager Glyn Edwards said the two subsidence incidents “aren’t linked”.

“They are not connected. They are two totally different types of geotech. They are two separate sites,” he said.

“This one here is wholly contained within the construction site.”

While he acknowledged the situation was “uncommon”, the tunnelling general manager said he didn’t think the formation of two sinkholes was “an extraordinary coincidence”.

CPB has already launched an investigation into the subsidence and it will not recommence work until SafeWork NSW and Transport for NSW give their approval.

“At present, we do not know the cause and we will not speculate about what the cause is,” Mr Edwards said.

“What we will be doing is making sure the site is safe and we will not be moving forwards until we have the methodology in place.”

CPB began to pump concrete into the sinkhole on Saturday afternoon and expects to complete the task by Sunday evening.

“Safety is basically our highest priority,” Mr Edwards said.

Deputy Secretary of Infrastructure and Place for Transport for NSW, Camilla Drover, said there had been no impact to the public or utilities as a result of the sinkhole.

A sinkhole opened up on March 1 underneath an industrial complex in southern Sydney.

The hole claimed parts of the building.

She said the department would now “take stock” and assess its options, but she didn’t expect to see any delays to the delivery of the M6 Tunnel Stage One.

“Our focus now is on the investigation and understanding what occurred but more importantly how we will go forward and complete the tunnelling,” Ms Drover said.

The assurances come nine days after the first sinkhole opened on West Botany St in Rockdale and shut down part of the Kirby Industrial Park.

Shocking images of the gaping hole show it swallowed part of the footpath and the ground underneath a building.

The building can be seen sagging in the middle after the ground beneath it vanished into the sinkhole.

Detailed geotechnical and engineering assessments will be undertaken at both sinkhole sites to determine whether it is safe to continue work.

Originally published as No connection between two sinkholes over troubled M6 project: contractor