‘Third Straw’ uncapped to provide Lake Mead water to Vegas

24 Sep 2015 | Author: | No comments yet »

‘Third Straw’ uncapped to provide Lake Mead water to Vegas.

The intake was unplugged Wednesday to finish flooding an $817 million tunnel and complete a complicated and perilous “Third Straw” project to draw drinking water for Las Vegas from a shrinking Lake Mead. Working from a barge floating on the reservoir, contractors pulled the cap off the deep-water intake late Wednesday morning, marking substantial completion of the seven-year, $817 million project that is being paid for in part through a series of rate hikes on local water customers. An 8.6-ton steel ball was hoisted to a barge, Southern Nevada Water Authority spokesman Bronson Mack said, in essence pulling the plug on a massive lake-bottom structure built somewhat like a big bathtub drain. “It’s a milestone. As recently as Sept. 10, project officials from the authority were predicting an early October start for the new intake, which will draw from the deepest part of Lake Mead, where the coolest, cleanest water is found. It involved excavating a 20-foot-tall tunnel beneath the bottom of the lake and connecting it to a buried concrete intake structure poking up from the lake bed three miles from shore.

First the tunnel had to be filled with about 52 million gallons of water to equalize the pressure with the surrounding lake, a process that began two weeks ago. A $25 million drilling rig the length of two football fields was lowered in pieces 600 feet underground and reassembled to chew through bedrock while inching along a set of rails.

The third intake — coupled with a $650 million pumping station due to be built over the next five years — will keep water flowing to the valley even if the lake shrinks low enough to dry out the community’s two existing straws. Wednesday marked the last major hurdle, though the contractor, Vegas Tunnel Constructors, is expected to remain on site through the end of the year removing equipment and finishing work on surface facilities above the intake’s access shaft. The pipes will deliver ammonia and chlorine to the mouth of the intake, where officials say they’ll mix to create chloramine — a compound that is used to eradicate quagga mussel larvae.

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