Lake Mead Intake No. 3 Southern Nevada Water Authority | 2010-2014
AUS is an integral part of the marine operations team for Lake Mead No.3 providing experienced personnel and state of the art equipment for the offshore riser installation. AUS provided a Falcon ROV, Trimble DGPS, Lindquist track point systems single beam and multi beam Mesotech Sonar systems. This subsea package is bundled into Hypac software for accurate barge positioning, shape charge blasting placement, dredging and excavation operations. The continuous monitoring allowed the progress to be mapped in tera model which enabled onsite adjustments to be determined quickly. AUS also provided conventional wet diving capabilities as required. The scope involved construction of an intake shaft in Lake Mead. Tasks 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 and the flared inlet installed. Finally, the top of the rock deflector cage was installed.
Divers were used 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.