Lake Mead: mechanized Tunnelling under high Pressure

摘要

Las Vegas the famous Nevada resort city with its casinos and entertainment-business, draws 90 percent of its water from Lake Mead. This largest reservoir in the United States is fed by the Colorado River. The areas around Las Vegas, however, are taking more from the lake than flows into it as snow melt and rain water from the Rocky Mountains. During the 14 years of drought, the water level has dropped by 35 m.The two existing water intakes for the Las Vegas Valley are in danger of running dry, and Intake No.1 could be at risk as early as this summer. It is now only 24 feet (7 m) below the lake level. The construction of a new, deeper water intake commissioned by the Southern Nevada Water Authority (SNWA) is a race against time. But the crucial section has been mastered: on December 10,2014, after three years of tunnelling, the Herrenknecht tunnel boring machine S-502 (O 7.2 m) reached its target on the lake bed.