The project features five different generations of Liebherr HS crawler cranes performing the main machinery tasks for the execution of the tunnelling. These machines in use are a HS 841 HD, HS 852 HD, HS 843, HS 855 HD and the latest, recently delivered HS 8070 HD.

The HS 8070, with 70t of load, is optimised to do all types of work on the construction site, being used both for excavation and concreting, as well as for the introduction of reinforcements. In addition, this model achieves significant reductions in fuel consumption and sound emissions and pollution, a determining factor especially for works in urban areas as is the case with this project.

The construction of the underground stretch of rail line is being carried out in a space of just 10m and just 3m from the train tracks that currently cross the city. In this very small space, 21m deep and 5m wide walls with circular joints and bentonite sludge are being created.