The challenging new Metro Barcelona Linea 9 Project where tunnels of up to 10.950m and 12.060m diameter are going to be bored under a high-density urban area, is bound to be commenced in spring 2003. Variable and difficult underground conditions will undoubtedly set higher and new standards of quality, safety and schedule meeting in the whole of the construction process: from the TBM technology and the boring process to the ground improving and monitoring. Two EPB shields and one dual hard rock/soil TBM will be used.