A boring diagram

by Sarah Gilman

Lake Mead -- Las Vegas' primary water supply -- has been drawing down like a leaky tub over the past decade, thanks to prolonged drought in the Colorado River Basin. The reservoir's now at 43 percent of capacity and about 100 feet below full -- just 45 feet above one of two main water intakes. If projections pan out, the water level could drop below that intake's pumping system by 2013. So the Southern Nevada Water Authority plans to spend the next three years and a total of $610 million digging under and up through the reservoir's bottom with a custom tunnel boring machine to build a new water intake, 190 feet below the one that must be replaced, and connect it to the existing water system.

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