Tunnel boring machine (TBM) Kathleen has dug more than 550 metres of tunnelling under the Sydney Harbour.
The tunnels will create the first metro rail crossing from Barangaroo to Blues Point.
The TBM is currently in soft sediment about 40 metres under the surface of the harbour and is progressing to hard rock conditions.
The machine uses compressed air to operate in soft material found in this section of the harbour.
During tunnelling there may be some visible water activity on the surface as the machine heads to harder materials.
Kathleen was launched on 2 August 2019 and is expected to take about four months to complete the first one kilometre tunnel.
The TBM will be lifted out at Blues Point and placed on a barge to return to Barangaroo, with the support trailers pulled back inside the first tunnel.
It will then complete the second tunnel under Sydney Harbour which will form part of the 15.5 kilometres of rail tunnels for the Sydney Metro project.
TBM Kathleen is named after Kathleen Butler who played a vital role in the construction of the Sydney Harbour Bridge as a technical advisor to engineer John JJC Bradfield.