The railway line from Madrid via Leon to Gijon on the Spanish Atlantic coast crosses the Cantabrian Mountains. The central mountain chain, the Picos de Europa, rise up to 2,648 meters. The trains have to take twisting routes through valleys and over high passes. The new route with the double-tube Pajares Tunnel will speed up the fright and person traffic on this vital connetion. The Pajares Tunnel is one of the longest in Europe with a length of 24.5 kilometers.
To master this major project, a Single Shield TBM and a Double Shield TBM were launched in July and September 2005, respectively. The Single Shield (S-287) bored its way from the south through the mountains. The machine accomplished breakthrough after over 15 kilometers in August 2008. From the intermediat addit at Folledo-Viadangos, S-281, the second machine, first excavated a five kilometer long access ramp followed by two tunnels each of 3.9 kilometers running parallel to each other. S-281 achieved the breakthrough in November 2007.
The Single Shield continued its tunnelling mission successfully on the northern Pajares-Sotiello lot after an extensive refurbishment and a customization. From July 2009 to March 2010, 5.9 kilometers of new railway tunnel were produced.