Mega borer Kathleen arrives to dig deep under Sydney Harbour

Tunnel boring machine Kathleen is being assembled at the site of the new Barangaroo metro station, ready for action in coming months to start tunnelling 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.

Specially designed for the geological conditions under Sydney Harbour, the 975 tonne machine will dig twin metro rail tunnels from Barangaroo to Blues Point.

Kathleen arrived by ship at White Bay and was transported by barge to Barangaroo Station near Hickson Road.

Kathleen will start her journey deep underground later this year from a massive cavern next to Barangaroo Station, which is being built to allow metro trains to cross from one rail line to another.

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, which 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.

Each tunnel is about one kilometre long.

Traditionally tunnellers look to St Barbara for protection and tunnel boring machines are given female names.

In 1924, John Bradfield acknowledged the incredible work done by Kathleen Butler as his only assistant in preparing the specification for Sydney Harbour Bridge.

Ms Butler was the first woman in Australia to have such a senior role in managing a project of this scale.

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.