THE first of two tunnel boring machines making their way underground from Forrestfield to the Perth Airport broke ground at Airport Central station last week.
TBM Grace broke through into the station box on Tuesday, May 8 after nine months and 1.9km travelled.
There were 15 workers inside the machine to guide it through a 12.5m concrete false block, used to stabilise the walls and reduce water getting in.
Grace stopped tunnelling on February 14 after encountering ground disturbance issues.
The second machine, Sandy, stopped on March 28 when it came within 40m of TBM Grace.
In a statement the Public Transport Authority said contractors had undertaken a detailed review of operating procedures as a result of the incidents.
“Specialist advisers from the TBM manufacturer have visited the site to review tunnelling operations,” the statement said.
“An independent international expert has been engaged to review tunnelling procedures and ensure lessons learned are incorporated into operations.”
An area known as The Ascot Formation, made up of non-cohesive granular material, complicated the tunneling process.
The issues were investigated and changes made to reduce the risk of further disturbances.
TBM Grace restarted on April 17 and TBM Sandy restarted on April 24.
The two TBMs will each tunnel eight kilometres under Perth Airport and the Swan River, linking to the new Forrestfield, Airport Central and Redcliffe stations.
TBM Sandy is due to arrive at Airport Central station later this month.
To find out more about the tunnel boring machines and the project, register to attend an information session on Sunday, May 27.
The project briefing centre includes a 4m model of the TBMs, photos and videos.
The event will run for about one-and-a-half hours and include a presentation and question time.