The 2,087m underground section includes the construction of two stations, Concha and Easo.
The €53.2m (£45.8m) contract has been awarded by the Basque Government, through the public body Euskal Trenbide Sarea (ETS). The consortium, which also includes Campezo, Mariezcurrena and Zubieder, will build the Miraconcha - Easo urban section of the Topo rail line in its passage through the centre of San Sebastián.
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