On 25 August 2010, around 13:10 CET, breakthrough was achieved in the eastern tunnel. Drilling then switched to the western tunnel, which started in March 2011 from the workface at the south end and proceeded north. On 3 April 2012, this drive reached the central adit, whereupon , or 46 percent, of the western tunnel had been bored. The remaining to be drilled, which totaled 15 percent of the entire drilling project, was expected to be particularly challenging, as it contains a section of poor quality bedrock and significant amounts of water and water pressure. An extra freezing stage, plus extra time (4 to 6 months) allotted for freezing, and thicker concrete lining segments, was utilized in this problem area, which is longer than the adjacent area encountered in the eastern bore. On 4 September 2013, the second tunnel broke through.