On 13 April last FCC concluded the excavation work on Terrassa Tunnel, which had to be done with the second TBM. The event took place in the presence of the head of the Department of Public Works and Territorial Policy of the regional government of Catalonia, Joaquín Nadal, Terrassa Mayor Pere Navarro and several executive officers from the Department of Public Works and Territorial Policy, the company Gestió d'Infraestructuras S.A. (GISA), and the builders that are partnered with FCC in the joint venture.

There are two parallel 3,150-metre-long tunnels with an excavation diameter of 6.9 metres. They are sheathed with 30-centimetre-thick concrete segments of tunnel lining and connected to one another by eight smaller cross-tunnels whose walls are shotcrete over a structure of wire mesh and trusses. The excavation cuts through a widely varying range of terrain types formed in the Quaternary period and the Miocene epoch, where clay and silt predominate, dashed through sporadically with sand and gravel.

The average depth of earth covering the tunnel's layout is between 14 and 20 metres, with a few exceptions such as the intersection with the existing RENFE tunnel and under the Torrent de Valparadís, where the covering layer is no more than five metres deep.