UPDATE - The Clark County coroner has identified the worker killed Monday as Thomas Albert Turner, 44, of Henderson. More ...
One man was killed and another injured in an accident at the third intake construction site 600 feet underground at Lake Mead on Monday afternoon.
Scott Huntley, spokesman for the Southern Nevada Water Authority, said the two men were struck by a jet of grouting material as they assembled concrete pipe segments in the underground tunnel about 4:30 p.m.
The man who was killed worked for Vegas Tunnel Constructors, the contractor hired by the authority to design and build the project.
He was part of a crew of 12 men installing the concrete pipe segments that ring the tunnel, water authority spokesman Bronson Mack said.
During installation, one of the six 20-foot-long segments jarred loose, releasing the pressurized liquid grout behind it, he said.
One of the men suffered only minor injuries, but the other was struck in the head and killed.
"His family is in our prayers," Mack said.
The rest of the crew evacuated safely and was never trapped or exposed to toxic gas, he said.
Workers' vehicles began leaving the site about 2½ hours after the accident. One vehicle stopped, and a tall man with a crew cut wearing a Vegas Tunnel Constructors T-shirt approached the assembled media demanding to know who was in charge.
"That was my brother that was killed in there. He was one of the hardest workers on the job," he said.
He then demanded the reporters "get their facts straight" instead of putting out "a bunch of lies," referring to early TV news reports of trapped workers.
He said his mother could have been watching the erroneous reports . When asked for his name, he said, "None of your business," and he walked away.
The project will remain on hold until an investigation is conducted by the contractor, the water authority and the state Occupational Health and Safety Administration, Mack said.
Water authority chief Pat Mulroy has called the third intake the most complicated construction job in the country.
Before Monday, the roughly $800 million project already had suffered several major setbacks, but none involving death or critical injury.
To reach the wet and muggy work area beneath Lake Mead's Saddle Island, miners have to descend to the bottom of a vertical access shaft roughly the same height as a 55-story building.
Groundwater, some of it heated by unseen volcanic features, seeps into the shaft and rains down on the tunnel.
Flooding poses the biggest risk on a project like this, but the job would be dicey even if it didn't cross directly beneath almost 4 trillion gallons of water.
As Marc Jensen, director of engineering for the water authority, told the Review-Journal in 2009: "It's a mining operation. You're underground under a whole lot of rock. This is a very risky project."
The job requires workers to drill a tunnel 23 feet high and three miles long underneath the bed of the nation's largest man-made reservoir.
Most of the digging will be done by a 1,500-ton tunnel-boring machine that chews away at the rock. The concrete intake pipe is assembled one ring at a time behind the machine as it creeps forward.
Each ring is made up of six concrete segments like the one that came loose from the tunnel wall Monday. It will take roughly 2,500 rings, each weighing about 34,000 pounds, to line all three miles of tunnel.
So far, the $25 million tunnel boring machine has advanced about 1,000 feet, said James McDonald, project director for Vegas Tunnel Constructors.
McDonald said there wasn't anything more he could say about Monday's accident beyond what the water authority had reported.
The new intake is being built to draw from the deepest part of Lake Mead and keep water flowing to the Las Vegas Valley in case the reservoir shrinks low enough to shut down one of the community's two existing straws.
The valley depends on Lake Mead for 90 percent of its drinking water supply.
Work on the third intake already was about three months behind schedule on July 1, 2010, when a crew excavating the starter tunnel for the boring machine hit a fault zone, causing water and debris to flood the work area.
Vegas Tunnel Constructors spent weeks trying to stabilize the fault, but the area flooded twice more. The contractor abandoned that tunnel and excavated a new one in a different direction in hopes of skirting the troublesome fault line.
To get the project back on track, the water authority board voted in February 2011 to add another $39.5 million to what already was the single largest construction contract the agency ever issued.
The change order also extended the timeline for the project by 593 days to the summer of 2014.
Review-Journal writer Brian Haynes contributed to this report. Contact Henry Brean at email@example.com or 702-383-0350.