History has been made deep under the heart of Sydney’s CBD with the first mega tunnel boring machine (TBM) arriving at the new Pitt Street metro railway station.

TBM Nancy broke through a wall of rock at the site of the future Pitt Street Station, about 20m below the streets of Sydney.

Nancy is one of five TBMs and has tunnelled six kilometres since launching in October at Marrickville. Since then, she has excavated about 600,000 tonnes of rock, or enough to fill 14 Olympic swimming pools.

At Pitt Street Station, it has taken nine months to remove about 92,000 tonnes of sandstone to build the underground station cavern in preparation for TBM Nancy’s arrival.

The 150-metre-long TBM will undergo maintenance before being re-launched towards the future Sydney Metro station at Martin Place, before moving on to Barangaroo.

TBM Mum Shirl is a few hundred metres behind Nancy, building the twin tunnel along the same route.

All the crushed rock from Sydney Metro tunnelling will be reused in other major local infrastructure projects, including in construction of the new Western Sydney International (Nancy-Bird Walton) Airport (see previous story).