In 1970, the consortium formed by the companies IECO (from the United States) and ELC Electroconsult S.p.A. (from Italy) won the international competition for the realization of the viability studies and for the elaboration of the construction project.
En 1970, o consorcio formado polas empresas IECO (dos Estados Unidos de América) e ELC (da Italia) venceu a concorrencia internacional para a realización dos estudos de viabilidade e para a elaboración do proxecto da obra.