 On 16 October 1910 the new deviation was opened for traffic and the Great Zig Zag closed.During World War II, the Clarence Tunnel on the Lithgow Zig Zag (along with other tunnels on various lines) were used to store chemical weapons for the Royal Australian Air Force.Principally mustard gas and phosgene, the chemical agents were housed in a variety of weapons from bombs to cylinders.