This tender covers the construction works for the Southern Railway Bypass of Bilbao (Variante Sur Ferroviaria de Bilbao), Phase 1, covering the section between Orconera and Durañona. The project involves railway tunnel and civil infrastructure construction works as part of a major rail infrastructure development in the Basque Country, Spain. The procuring entity is Euskal Trenbide Sarea (ETS), the Basque Railway Network authority.