1998-1999
The project for Lake Mead No.2 involved construction of an intake shaft in Lake Mead. Tasks performed by AUS included installation of a rock deflector cage, flared inlet, and 12-foot diameter steel-lined shaft in depths up to 240 feet below the lake surface and 380 feet offshore. The intake site was located immediately below a 600-foot high steep rocky hill, with the lower 240 feet below water. Underwater construction of the shaft was based on original design and construction concepts pioneered in 1990 for the Roosevelt Dam Lake Tap Project. It involved several stages: First, the intake shaft was constructed downward working from the lake surface. When completed, a temporary stainless steel cap was installed to seal it off. Second, the intake tunnel was driven eastward to connect to the bottom of the shaft. Third, the tunnel and shaft were flooded. Fourth, the stainless steel cap was removed, the flared inlet installed. And finally, the top of the rock deflector cage was installed. Divers were utilized for both topside support and diving operations. The dive barge supporting operations included two decompression chambers, a remote operated vehicle, an ROV control shack, a diver control shack, diver equipment shack, contractor office, inspector office, helium tanks, oxygen tanks, and a wet bell winch to transport divers between the lake bottom and the barge.
