Eiffage Energía is performing work on the 400 kV underground line for the Gouvaes Hydroelectric Power Station, on the Tâmega river in Portugal. The project will house four 400 kW generators, a transformer cavern with a length of 80 metres; and a vertical pit, with a maximum height of 300 metres and a diameter of 7 metres. The work consists of installing fittings in the gallery, pit and transformer cavern; laying earthing cables; and laying the underground power cable for the four 400 kV circuits. The underground cable is being laid in three parts. From the Gis substation, passing through the sloping pit access gallery; the installation of 300 vertical metres in the pit; and the transformer cavern gallery. A total of around 900 supports will be installed, where the cables will be housed in their final positions, and around 9000 metres of 400 kV cable will be laid.