Lake mishap 'not devastating'


The Las Vegas Valley won't run short of water because of a recent accident at the site of a new intake straw at Lake Mead, Southern Nevada Water Authority chief Pat Mulroy said.

Officials still don't know how long the project will be stalled by the July 1 mishap, but Mulroy said that even under the worst of circumstances the valley will have enough water to get it through 2013, when the intake originally was scheduled to go on line.

Water authority board members were briefed on the setback Thursday.

Marc Jensen, director of engineering for the water authority, told board members it is "too early to say with any certainty" how much time and money it will take to get the $700 million project back on track.

After the meeting, Jensen said he is "still optimistic" that the new intake will be finished by the end of 2013.

The accident occurred when workers excavating a cavern 600 feet underground hit a fault zone, causing water and muck to pour into the work area.

Efforts to seal off the fault proved unsuccessful, and the entire cavern quickly filled with water and debris.

"We were extremely fortunate there was no loss of life and no workers were injured," Mulroy said.

Jensen said "at least a half dozen" pieces of mining equipment were lost underground after the workers "retreated" to the surface and the work area flooded.

"It's unfortunate, but it's not devastating," he said. "We can recover and we will recover."

Mulroy has previously described construction of the so-called third straw as a "race against time," as Lake Mead threatens to shrink below the two existing intakes that supply the valley with 90 percent of its drinking water.

On Thursday, though, she said even if the reservoir continues to fall and the valley's growth spikes back up, enough water is available to meet peak demand.

The authority may need to turn on all of its groundwater wells in Las Vegas and North Las Vegas, she said, but "we can get through the summer of 2013."

Construction of the third intake involves mining a three-mile tunnel beneath the reservoir and connecting it to an intake structure that will stick up from the bed of Lake Mead at one of the deepest spots in the reservoir's Boulder Basin.

Workers have spent the past two years excavating a 600-foot vertical access shaft and an underground cavern to accommodate the massive tunnel boring machine that will dig the three-mile intake tunnel.

The cavern was supposed to be finished and the boring machine in place by now, but the work was already about three months behind schedule before the July 1 accident, Jensen said.

He said such a lag in a job this large and complex is "well within the range of expectation."

"It's a risky construction project," Jensen said.

Vegas Tunnel Constructors, the project's general contractor, is now trying to stabilize the fault zone so excavation can resume.

The plan is to drill down from the surface and pump grout into the fractured rock. If that works, the cavern can be "mucked out" and drained of water, and the miners can go back down the shaft to continue their work 600 feet beneath the surface.

Contact reporter Henry Brean at hbrean@reviewjournal.com or 702-383-0350.

 

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