"It was extremely warm [inside the tunnels]. Concrete is normally hot. And it was extremely warm back there. I remember when we were pouring the plug I think it was in the Number 3 tunnel on the Arizona side, the one closer to the river. They say the temperature got up to 150,160 degrees back in there, and the men were working. They'd go back in and work for 15 minutes, come out and rest for 15 minutes, back and forth like that. - Carl Merrill "It was like a movie of Tarzan, you know. You'd hear the blast and then see those guys fling themselves down there and start ripping the rocks off, and there were people above them and people below them. "55 -Ila Clements-Davey Finally an arch jumbo was built to set in the arch (or top) sections. The concrete was either hauled or pumped in to complete the tunnel with a circle. During the excavation phase, hundreds of visitors daily viewed the spectacular panorama of men and machines spread before them in Black Canyon