Metro tunnelling completed under Sydney Harbour

All Sydney metro tunneling works are completed for the new twin tunnels on the Sydney Metro City & Southwest project.

Mega boring machine Kathleen has broken through a wall at north of the harbor, tunnelling two 885-metre-long tunnels from Barangaroo to Blues Point.

It took two months to build the second tunnel, one month faster than the first tunnel, due to lessons learned like modifying the giant cutter head and changing tunnelling processes to better deal with the clay material at the bottom of the harbour.

TBM Kathleen dug through about 175,000 tonnes of sandstone, clay and marine sediments to build both harbour tunnels, which are about 40 metres below sea level at their deepest point.

The five TBMs on this project have delivered 31 km of fully lined tunnels in only 17 months.

From the north west, metro rail is being extended under Sydney Harbour, through new underground city stations and beyond to the south west.

In 2024, Sydney will have a 66-km metro system served by 31 stations.

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