Tunnel 3 belongs to the Donostia-Hendaia line of the conventional Basque Railway Network - Euskal Trenbide Sarea, (ETS) and is located in Donosti, in the province of Gipuzkoa, between the stations of Herrera and Pasaia.
It is a 368-meter-long, electrified single-track tunnel under the town center, with a masonry support-lining element in the vast majority of the tunnel.
The reinforcement and stabilization works have been carried out in a section between PP.KK. 6+235 to 6+270 with shotcrete reinforced with polypropylene fibers and placement of twenty-five millimeter passive bolts.
These works were carried out in maintenance band (night time), without railway traffic cut.