TUNNELLING for the Forrestfield-Airport Link has been stalled for more than a month after work caused two sinkholes near Perth Airport.

WA Transport Minister Rita Saffioti confirmed yesterday that boring machine Grace was forced to stop on February 14 after two disturbances in the earth above the tunnel, 300m from the airport station site.

She said that while an independent precautionary review was being done of the site, Grace would undergo maintenance after tunnelling for 1.6km.

“It’s quite a tricky ground formation in the area,” Ms Saffioti said.

“You’re moving from sand to clay to rock, so as a result it was always going to be a challenge to make sure it got through cleanly.

“We want to make sure that everything’s clear to go forward, so they’re doing a review as to how everything was operating in that area.

“There’s no delay yet because Grace was ahead of schedule and it was waiting for the (station) wall to be completed.”

A Perth Airport spokeswoman said there had been no threat to workers or the public and the project had not reached any critical infrastructure.

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“The temporary suspension will allow for the processes associated with the tunnelling to be independently reviewed and validated,” she said.

“PTA and Perth Airport will work together to progress the review in a timely manner to allow for resumption of tunnelling. Following discussions with Perth Airport and the Public Transport Authority, the contractor chose to cease tunnelling.”

Opposition Leader Mike Nahan accused the Government of attempting to hide the fact the boring machine had stopped.

“It’s been offline for weeks and all I can say is that the McGowan Government was elected on the basis of gold-standard transparency,” he said. “The public has every right to know if the borer is working. After all, they had a contest to name the borer.”

Ms Saffioti said the second boring machine, Stacey, would continue tunnelling work.