The second of the Forrestfield-Airport Link’s two tunnel-boring machines (TBMs) has been temporarily halted, following the first machine being forced to stop in February 2018.
TBM Sandy was stopped when it came within 40m – the minimum distance – of the stationary TBM Grace.
Grace stopped tunnelling on 14 February 2018 after encountering some minor ground disturbance issues when travelling through difficult terrain, the Ascot formation.
Though Sandy has not experienced the same ground disturbance issues, it is widely-accepted best practice that two TBMs should not be positioned side-by-side during tunnelling.
The tunnelling contractor is undertaking a detailed review of operating procedures as a result of the incidents with Grace.
Specialist advisers from the TBM manufacturer have visited the site to review tunnelling operations.
An independent international expert has also 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.
It is expected that Grace – and subsequently Sandy – will be able to resume tunnelling in mid April 2018 once a number of investigations into the earlier ground disturbances are complete.
Work will continue on the construction of Airport Central Station and the dive structure at Bayswater Junction.