The first of two railway tunnels to be built under Sydney Harbour, as part of the Sydney metro project, has been completed.
At its deepest point, the tunnel is 40 metres below the harbour floor and is considered “an engineering feat of historic proportions,” according to NSW premier Gladys Berejiklian who visited the site of the tunnel on Monday.
Specialised under-harbour tunnelling boring machine (TBM) Kathleen will dig the two tunnels. TBM Kathleen launched in June, from Barangaroo Station, and took four months to tunnel nearly one kilometre to the northern side of the harbour at Blues Point.
After completing the first of the two tunnels, the TBM was then pulled apart and had its giant 90-tonne cutter head and front sections barged back across Sydney Harbour, from where it is now being reassembled to start digging the second tunnel. The 975-tonne machine had removed 87,400 tonnes of sandstone, clay and marine sediments to dig the first tunnel.
Metro trains will start running through the two tunnels in 2024. In 2024, Sydney will have 31 metro stations and a 66km standalone metro railway, with the capacity for a train every two minutes in each direction. It will be able to move more people across the harbour in the busiest hour of the peak than the Harbour Bridge and Harbour Tunnel combined.
Another TBM, Wendy has reached the harbour’s edge at Blues Point, making her the first of the five mega borers to officially finish tunnelling on the Sydney Metro City & Southwest project. TBM Wendy completed a 6.2 kilometre tunnel via new stations at Crows Nest and Victoria Cross, excavating 563,000 tonnes of sandstone and shale.
Kathleen and Wendy are two of five mega borers which have worked simultaneously to deliver the twin 15.5 kilometre rail tunnels between Chatswood and Sydenham, extending Metro rail from the north west, under the CBD, and beyond to Bankstown.