Because Las Vegas obtains roughly 90 percent of its water from Lake Mead, the construction of Lake Mead Intake No. 3 helps to assure adequate water supply for future generations. Over the last 10 years, drought conditions across the western United States contributed to a declining water level in Lake Mead of approximately 100 feet. The new water intake facilitates added a much-needed water supply capacity for Las Vegas. Accessed from a shaft at a depth of approximately 560 feet, the new intake extends approximately 3 miles to a riser excavated in a cavern at the bottom of Lake Mead.
Atkins performed verification surveys of the project control using high-order differential GPS. In addition, after densifying control around the shaft, we transferred control to the starter tunnel using specialized survey gear such as Baechler prisms, Taylor Hobson spheres, and ZL plummets. Atkins also verified the tunnel alignment by providing accurate gyro-azimuth observations using the DMT Gyromat 2000. The shaft transfer technique enabled horizontal and vertical control transfer to an accuracy of 0.005 feet. The Gyromat 2000 provided survey control accuracy within an impressive 3 arcseconds.