A small leak occurred around a cross passage adjacent to Dundas Road, which led to the formation of a sinkhole earlier this week and the closure of the road.
Works are ensuring ground water does not leak into tunnel one at the throughway to connect the two tunnels, which will be used as an emergency exit once the rail line is operational.
The tunnel boring machines have stopped as a precautionary measure while a survey of the ground along Dundas Road and the tunnel connecting to the cross passage is underway.
As a result of the leak, there has been movement of around 10 tunnel rings near the cross passage, with additional internal bracing now in place to stop the leak and resolve the sinkhole damage.
WA Transport Minister Rita Saffioti said the state government is monitoring the situation closely with Salini-Impregilo – NRW Joint Venture.
“My number one priority is to ensure work is carried out safely,” Ms Saffioti said.
“I have asked the Public Transport Authority to review the timeline of the project, to ensure worker safety is paramount.
“In addition, there will be a review into the method used to create future cross passages and surveys are now being undertaken of the ground and the two tunnels in the vicinity of this particular cross passage.”