Tunnel hole-through, also called breakthrough, is the time, during the construction of a tunnel built from both ends, when the ends meet, and the accuracy of the survey work becomes evident. Many tunnels report breakthroughs with an error of only a few inches, for example: the 1858 Blue Ridge Tunnel – the 1944 Blue Ridge Tunnel replacement – - 1944 the Lötschberg Base Tunnel – 10 cm the Holland Tunnel - 1 cm See also Cascade Tunnel References External links Gautrain tunnel breakthrough Brisbane Clem 7 Gotthard tunnel Lotschberg - 10 cm Tunnel construction