Contractor Vegas Tunnel Constructors (VTC), a jv of Impregilo and its subsidiary S.A. Healy, have driven the 23.5ft diameter machine some 4.5km as part of a project to take a third intake at Lake Mead, providing water for the region.
The project faced difficult ground, and has seen pressures as high as 14.5bar. VTC launched the machine in 2011, following a number of faults requiring realignment of the starter tunnel.
