Construction crews hit water on July 6 while digging 600 ft below Lake Mead in southern Nevada for the third “straw” water tunnel. The incident, which was not life-threatening, will delay the project’s progress by months. Vegas Tunnel Constructors LLC––a joint venture of S.A. Healy Co., Lombard, Ill., and Impreglio S.p.A., Sesto San Giovanni, Italy ––won the $447-million design-build contract in March 2008. On June 28, an underground fault breached, causing water seepage for four days and making work in the tunnel impossible. Workers were building a 100-ft-long starter shaft for the $25-million Herrenknecht 1,500-ton tunnel-boring machine for a 20-ft-dia, 3-mile tunnel beneath the lake. The water problem is being brought under control by portable pumps that remove up to 400 gallons per minute. Contractors will drill north of the shaft to locate the soft rock and pump in reinforcing grout to stabilize geotechnical conditions.
Water Seepage Delays Nevada’s ‘Third Straw’ Water Tunnel
July 14, 2010