Drought-racked Las Vegas is undertaking an emergency project to keep water flowing as Lake Mead’s capacity dips below 40%.
The Southern Nevada Water Authority has planned a $12-million extension to its 42-year-old raw-water Intake No. 1, which faces inoperability if the lake level falls 40 ft. Federal forecasters expect that to occur by May 2015 or sooner because of an abnormally dry winter.
Lake Mead’s surface level dropped to 1,106 ft in August, or 108 ft lower than 2000's level, reports the U.S. Bureau of Reclamation.
The water authority says its seven-month drill-and-blast project, which will deepen the intake by 110 ft, should provide the stopgap insurance against the region running dry. About 90% of Clark County’s two million residents rely upon Lake Mead water.
The 9-ft x 21-ft intake extension will connect to a newly finished, half-mile-long, $52-million stub tunnel, completed by Renda Pacific, that will link Intake No. 2 and a third intake that is still under construction.
Renda Pacific will perform extension work as a change order, pending a Sept. 26 water-authority board vote.
The tunnel, which is being reinforced by shotcrete and rock bolts, should finish by May 31, 2014. The lengthened straw will help safeguard against federal emergency drought conditions.
Lake Mead is receiving its smallest-ever annual water allotment due to a sudden dip in Lake Powell fueled by the second-driest year since the drought began in 2000. A reduced release is expected the following year, too.
Meanwhile, Vegas Tunnel Constructors LLC—a joint venture of S.A. Healy Co., Lombard, Ill., and Impreglio S.p.A., Sesto San Giovanni, Italy—are constructing a $526.6-million third intake using a custom-built $25-million Herrenknecht tunnel- boring machine.
The three-mile-long, 20-ft-dia concrete-ring-lined tunnel will draw water from 860 ft, which is deeper than the two existing Lake Mead intakes.
The project, however, has suffered flooding setbacks, which have pushed likely completion to 2015.
