The Santolea Bridge tailing dam, built by the Presa de Santolea Joint Venture consisting of the firms Isolux-Corsán and Copisa, has been recognised as one of the best to be built in Europe and the finest in Spain. The almost flawless execution of this engineering work is due in large part to a work methodology that makes it possible to optimise the concrete mix, using the natural resources of the area and with the utmost respect for the environment.