The breakthrough of the eastern tunnel was achieved on 20 September 2007 at about 16 : 35 .
The breakthrough of the western tunnel followed on 1 October 2007 at 15 : 10 .
The breakthrough of the eastern tunnel was achieved on 20 September 2007 at about 16 : 35 and the breakthrough of the western tunnel followed on 1 October 2007 at 15 : 10 .