The Forrestfield Airport Link tunnelling also marks the longest rail tunnel ever attempted in WA.
TBM Grace set off from Forrestfield in July 2017 and has tunnelled under Perth Airport and the Swan River.
The machine tunnelled to depths of 26 metres in diverse ground conditions.
Grace will now be dismantled and craned out of the dive structure in preparation for the arrival of another TBM, Sandy, who is expected to break through later this year.
This will then mark the completion of tunnelling for the Salini Impregilo – NRW Joint Venture on the Forrestfield-Airport Link project.
Work is also continuing on important infrastructure such as station construction and fit out and preparing the tunnels for track laying.
Construction of the first stage of the track slab within the tunnels is more than 40 per cent complete. The second stage of the track slab, including installation of the rail, will start mid-2020.
Trains are expected to run on the new rail line in late 2021. It will provide a 20-minute rail link between the eastern foothills, Perth Airport and the city.