State safety regulators in southern Nevada on Tuesday began investigating a fatal construction accident in a water supply tunnel being built at Lake Mead, the latest in a series of mishaps and setbacks at the multi-million dollar project that began in 2009.
A Nevada Occupational Safety and Health Administration investigator visited the 3-foot-diameter tunnel where one man was killed and another injured about 4:30 p.m. Monday approximately 600 feet below ground near the Lake Mead National Recreation Area.
"State OSHA is investigating," Carrie Foley, executive assistant to the state agency's director, said Tuesday. "I can't answer any other questions right now because it is an open investigation."
Thomas Albert Turner, 44, of Henderson, and another worker were alone in a segment of the tunnel when they were hit by exploding grout material after some material became loose, officials for the Southern Nevada Water Authority said.
Turner was killed, while the second man sustained minor injuries, authority spokesman Bronson Mack said. An update on his condition was not available Tuesday and authorities had not confirmed his identity.
The tunnel is part of a troubled effort to drill a third drinking water supply line to the Lake Mead reservoir. The project has been hit with flooding and cave-ins since construction began in 2009, and work has been delayed by about two years.
Workers in other areas of the tunnel were not affected by Monday's accident. Early media reports that more than a dozen workers were trapped in a collapsed tunnel or exposed to toxic fumes were false, the water authority and OSHA officials said Tuesday.
"At no time were any workers trapped in the tunnel or exposed to toxic gases," said Steve Coffield, Nevada OSHA's chief administrative officer. He also said there was no flooding.
Las Vegas depends on Lake Mead for about 90 percent of its drinking water. Construction on the third tunnel began amid concerns over the Colorado River reservoir's shrinking supply. The third intake is designed to keep water flowing to Las Vegas even if drought shrinks the lake below the level of the two existing conduits.
The new tunnel, bored through solid rock beneath Lake Mead, will be 3 miles long.
"During the assembly of some segments of the tunnel ring, one of the segments became loose, and the grout material exploded and hit two workers," Southern Nevada Water Authority spokeswoman Nicole Lise said.
Mack said the tunnel is not flooded and is still intact. He said the water authority will conduct an investigation into the accident.
Clean-up operations continued at the site on Tuesday. It was unclear when construction might resume.
"Construction activities will not resume until the cause has been identified and corrected and the safety of the tunnel has been verified," Coffield said.
The project was delayed last year after a cavern 600 feet underground filled with water and muck. In another delay, some mining equipment was lost to flooding.
Associated Press Reno correspondent Scott Sonner contributed to this report.