Western Australia’s Public Transport Authority (PTA) has confirmed that the second of the tunnel boring machines (TBM) working on Perth’s Forrestfield-Airport Link has been temporarily halted.
The first TBM – Grace – stopped tunnelling on 15 February but the suspension of Salini Impregilo’s work on the bore for the new metro due to issues with ground conditions was only made public last week.
The second TBM – Sandy – has been stopped as it was within 40m of the first TBM, which is a preset minimum distance.
The PTA has said that Sandy has not experienced the same ground disturbance issues but had been stopped to avoid the TBMs being positioned side by side in accordance with best practice.
TBM manufacturer Herrenknecht with working with tunnelling contractor Salini to undertake a detailed review of operating procedures as a result of the incident with Grace.
A spokesperson for PTA added: “An independent international expert has been engaged to review tunnelling procedures and ensure lessons learned are incorporated into operations.
“The Public Transport Authority, contractor Salini Impregilio, NRW and Perth Airport are working closely to allow full tunnelling operations to resume as soon as possible.”
The PTA said that it expects tunneling to resume within weeks.