In this June 1, 2015 file photo, a worker walks in a tunnel still under construction beneath Lake Mead near Boulder City, Nev. Flooding the tunnel has now been finished, and officials are opening the intake on a massive “Third Straw” project to draw drinking water for Las Vegas from a shrinking Lake Mead. An 8.6-ton steel cap will be hoisted Wednesday, Sept. 22, 2015 to a barge from a massive lake-bottom structure designed somewhat like a big bathtub drain. That’ll mark completion of a dangerous and sometimes frustrating six-year, $817 million Southern Nevada Water Authority drilling project to keep taps flowing even if Lake Mead drops to its lowest levels.(AP Photo/John Locher, File)