Sydney Metro Northwest is the first transport infrastructure project in Australian history to use for tunnel boring machines (TBMs) at once, delivering the twin 15 kilometre railway tunnels between Bella Vista and Epping. After digging underground for 10 months, TBM3 Isabelle reached the end of the line on 18 September – breaking through at Epping and becoming the first of Sydney Metro Northwest’s four tunnel boring machines to complete her journey. Isabelle completed her journey from Cherrybrook after digging almost 6 kilometres including the deepest section of the new railway tunnels, 58 metres below Thompson’s Corner at West Pennant Hills. One year of tunnelling on Australia’s biggest public transport project was marked with TBM1 Elizabeth - the first of the project’s four tunnel boring machines - arriving at Castle Hill. Elizabeth started digging from Bella Vista on September 8 last year and after travelling 6.5 kilometres in 12 months, broke through into the site of the future Castle Hill station on September 9. As well, we marked a rare event in the world of tunnelling with Maria - the project’s fourth tunnel boring machine - literally popping its head up for air at Cheltenham. Most tunnel boring machines arrive “face first” at a site, breaking through a wall of rock. But at Cheltenham, Maria, and her sister Isabelle before her, only stuck the top 3 metres of their cutter-heads out – then kept on tunnelling through the site. The Cheltenham site will be used for fresh air tunnel ventilation and as an emergency access point to the tunnels below when metro trains start operating in 2019.