Tunnel Boring Machine (TBM) Kathleen has passed its final inspection and is now ready to launch from Barangaroo next month to dig the historic rail crossing deep under Sydney Harbour.

The 975 tonne tunnel boring machine was assembled deep under Barangaroo and will soon start digging the first of twin one-kilometre tunnels, 40 metres below the Harbour at its deepest.

After building the first tunnel, TBM Kathleen will have her giant cutter head and main section lifted out at Blues Point and placed on a barge to return to Barangaroo. The machine’s support trailers will be pulled back to Barangaroo inside the first tunnel.

Kathleen will then build the second tunnel under Sydney Harbour after that, the whole TBM will be retrieved at Blues Point and taken away by barge. The machine is expected to tunnel through clay, silt and sediment and will use state-of-the-art tunnelling technology to safely make its way under the harbour.

This specialised TBM is named after Kathleen Butler, who played a vital role in the construction of the Sydney Harbour Bridge as the technical advisor to legendary engineer John JJC Bradfield.

TBM Kathleen will join the four borers currently digging from Marrickville and Chatswood towards the harbour’s edge.

Together, all five TBMs will deliver twin 15.5 kilometre rail tunnels for Australia’s biggest public transport project. For further information please visit https://www.sydneymetro.info/