Two drill rigs, installed on barges, have started work on the Hawkesbury River at Brooklyn and at Brisbane Water near Gosford

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Drill rigs have started boring into rocks and riverbeds to determine the best route for the tunnelling megaproject needed for a high-speed rail line between Sydney and Newcastle, but the fast train’s future is far from certain amid questions about its cost.

Almost three years after Labor came to power on a promise to build the fast train, two drill rigs have begun geotechnical examinations on the Central Coast of New South Wales, the Albanese government announced on Tuesday, as its newly formed High-Speed Rail Association (HSRA) works on a business case for the project’s first stage.