The Sestao-Portugalete section consists of approximately 1.64 km. of metric-gauge double track.

We laid 2,174 m. of track on a concreted plate with  UIC 54 rails and bi-block sleepers with elastic seating, according to the Stedef design, for embedding in concrete. We installed one B1-type double diagonal.

The works also included executing the drainage network and installing the dry standpipe.