Nine ventilation shafts and emergency exits were designed, and the railway tunnel was excavated with boring machines. Cladding was done with precast concrete voussoirs. The stations were built with reinforced concrete cut-off walls.
The new infrastructure consists of the excavation of a double-track tunnel by means of an earth pressure shield with a free diameter of 9.60 m, and 0.32 cm precast voussoirs. A 60 kg/m track with a width of 1,668 mm and a distance between axes of 3.82 m embedded in an elastomeric matrix is mounted on a concrete slab. On the sides of the track, there are several longitudinal 1-m paths under which the pipelines run.
The project included the construction of 8 ventilation shafts along the length of the tunnel, plus emergency exits, 2 of which will also house pumping wells and one ventilation shaft. The project includes the construction of 3 stations along the line, each with 165-m long platforms. Begoña Station will be built using mining methods, whereas the stations of El Bibio and Viesques will be built using a cut-and-cover method.
The electrification and the signalling and communications installations were not included in the project. The project also did not cover any tunnel ventilation or lighting components, cladding, finishing, or building installation.