One of the Mack trucks in front of the upper portal of Diversion Tunnel #2. This truck has 9 cubic yards capacity. Note the steel canopies over the driver's heads on all the trucks. Jan. 28, 1932.
A flashlight photograph of the interior of one of the diversion tunnels. The drilling jumbo is working at the tunnel face. The 12' by 12' top-heading can be plainly seen. January 28, 1932.
One of the drilling jumbos ready for action. This view was posed outside the tunnel, just as the swing shift was ready to go to work on the upper portal of Diversion Tunnel #1. January 28, 1932.
Drilling jumbos (aka Williams Jumbo) mounted on the back of a truck for starting construction of lower portal No. 4, Arizona side of Black Canyon. 9-26-31. (This first wood-frame jumbo was experimental - the jumbos later were steel pipe)