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Authorities are investigating the death of a worker who was struck by a high-pressure stream of grout in a tunnel project more than 600 feet below Lake Mead, NV.
Thomas Albert Turner, 44, of Henderson, NV, died and another worker was injured late Monday when the jet of grout, mud and rocks shot from a pipe on which they were working, officials said.
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Images: Vegas Tunnel Constructors |
| The access shaft to the tunnel site is 611 feet deep. The intake structure is being built 300 feet below Lake Mead. |
Turner worked for Vegas Tunnel Constructors on the $800 million project to drill a third drinking-water supply line to the Lake Mead reservoir. The centerpiece of that project involves digging a tunnel 23 feet in diameter and three miles long.
The troubled project has seen repeated flooding and mishaps and is now two years behind schedule.
Nevada OSHA has halted work at the site while it investigates Turner’s death.
‘Jarred Loose’
The Southern Nevada Water Authority (SNWA) and the contractor said in a joint statement that three crew members had been setting concrete ring segments at the SNWA Intake No. 3 project area at Lake Mead when the segment “slipped forward, allowing pressurized grout to force through” a four-inch by two-foot gap.
In another statement, authorities said the tunnel segment “was jarred loose.”
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| An official calls the project the most complicated in the country. Tunnel boring has progressed only about 1,000 feet, and the project is months behind schedule. |
About one-half of a cubic yard of mud, grout and rocks blew out with about five times the force of a garden hose running full blast, said SNWA spokesman Scott Huntley. Some of the rocks in the mix were two to four inches across. Turner was struck in the head.
Crews had previously installed 133 of the tunnel’s nearly 2,500 rings without incident, the statement said. The concrete intake pipe is assembled one ring at a time behind a 1,500-ton tunnel boring the machine as it creeps forward. Each 34,000-pound ring consists of six concrete segments.
Water authority chief Pat Mulroy has called the project the most complicated construction job in the country.
‘A Difficult Time’
The grout is used to fill the three-foot space between the tunnel’s rock walls and the concrete pipe. For the grout to work, it has to be pressurized to about 200 pounds per square inch, Huntley told the Las Vegas Review-Journal.
“VTC is investigating how the one segment slipped forward and how to prevent such slippage from happening in the future,” the statement said. “Tunneling activities will not resume until that determination is complete.”
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| Vegas Tunnel Constructors, a joint venture formed for the project, is working under a $447 million contract. |
The statement added: “This is a difficult time for our organization, the contractor and the crew. At no time were any workers trapped in the tunnel or exposed to toxic gases. All other workers have been accounted for and are safe above ground. Furthermore, there was no flooding of the tunnel.”
On Monday evening, Vegas Tunnel Constructors’ Tunnel Rescue Team descended into the tunnel and examined the accident site. The VTC team determined the tunnel was safe for entry. A Nevada OSHA team then conducted an initial inspection Tuesday morning before allowing VTC to secure and clean the area.
New Joint Venture
Vegas Tunnel Constructors was formed in 2007 to build the intake. The joint venture by S.A. Healy and Impregilo S.p.A. is working under a $447 million contract awarded in March 2008.
Federal OSHA records show the project has been inspected eight times since August 2008. Three inspections were triggered by complaints; one, by an accident; and four by referrals.
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Local 872 |
| Members of Local 872 train for the tunnel work, which began in 2008. Thomas Turner was a member of the local. |
Two inspections resulted in multiple citations. In October 2009, the contractor was issued two serious and three other-than-serious citations for safety violations and fined $6,500. That was later reduced to two other-than-serious violations and an $800 fine.
In July 2010, the contractor was issued seven serious and two “other” violations and fined $6,800 after the site was flooded with water and debris The case was later reduced to three “other” violations; the final penalty was not listed in OSHA records.
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