Tunnel boring machine (TBM) Sandy has joined TBM Grace on an underground journey from Forrestfield.TBM Sandy was named by High Wycombe Primary School Year 4 student Sarah Spratt after our local digging insect the 'Sandgroper'.

TBM Grace , which launched on July 30, has now travelled around 620 metres and is currently travelling around 20 metres per day.

The two TBMs will each tunnel eight kilometres under Perth Airport and the Swan River, linking new stations at Forrestfield, Airport Central and Belmont. Construction of diaphragm walls (which will house the station box structure) is now complete at Airport Central , and excavation of the soil inside the walls has begun.

Diaphragm walls are also under construction at Belmont , and are about 70 per cent complete.

As the TBM cutter heads bore through the earth, the machines will install about 54,000 reinforced concrete tunnel segments, fabricated at a local Forrestfield segment facility.

More information is available on the Forrestfield-Airport Link website.