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Ground motion examined as factor in L.A. water main breaks

The investigation into what could be causing a sharp rise in “major blowouts” of Los Angeles water mains has expanded to examine whether tectonic activity might be playing a role.

The L.A. Department of Water and Power have asked scientists at the Jet Propulsion Laboratory for help. As it happened, JPL officials were already evaluating ground movement in the Los Angeles Basin because of a several recent minor earthquakes.

Examining the timing and location of the breaks, JPL scientists notice “some deviation from the normal range” of ground movement in L.A. in the last 100 days, said Andrea Donnellan, a geophysicist at JPL.

“We’re trying to understand,” she told The Times.

Donnellan said scientists concluded there has been a change in ground movement by using GPS data from sensors embedded in the ground across the Los Angeles Basin. 

The sensors have been in place for only a few years, however, so it’s difficult to say whether the movements of the last 100 days is really an anomaly.

The movement detected is fairly subtle and may not be directly related to any increase in the number or intensity of local earthquakes.

As a result, Donnellan said, it’s doubtful that ground movement is a primary cause of the water main breaks. Los Angeles has seen a surge in recent month in what engineers have called major blowouts in the city’s aging water system in which streets have flooded and pavement has buckled -- in some cases damaging homes and businesses.

City engineers are trying to determine what’s causing the breaks and have been taking soil samples, sending pipe pieces to labs for testing and performing a statistical analysis on each break.

While the DWP says it has not found a cause, experts have offered various theories. Some said a prime suspect should be the city’s recent decision to allow sprinklers to run only on Mondays and Thursdays.

They say that if more water flows through the system on those two days when people water their lawns and then pressure suddenly changes on other days, it could be putting added stress on already aging pipes.

The DWP said it’s too early to determine a cause. Officials confirmed that the DWP is seeking assistance from USC, JPL and Cornell University, bur declined to comment further.

As part of JPL’s effort, scientists will analyze radar data of ground movement taken from a NASA airplane.

Donnellan said it could be months before researchers have any answers. Engineers also stressed that the city’s 7,200 miles of pipe aren’t actually leaking more than usual -- in fact, the number of leaks, about 1,400 a year, is down from the past and represents a lower rate per mile of pipe than in other cities.

The problem is with bigger, more destructive leaks that send water shooting through streets. The matter came to the DWP’s attention Sept. 5, after a 5-foot-wide trunk line under Coldwater Canyon Avenue in Studio City exploded, sending a 10-foot gusher of water and mud into the air.

Homes and businesses were flooded, and the street, a major thoroughfare connecting the San Fernando Valley and the Westside, was closed for a week. That pipe was 95 years old and officials suspected that age may have been a factor in its failure.

Less than 72 hours later, another, newer main burst in Valley Village, creating a sinkhole that swallowed half of a fire truck that responded to the call.

Firefighters crawled out the window to safety. As officials analyzed those problems, they realized they had been seeing an increase in major blowouts.

-- Jessica Garrison

Photo: Coldwater Canyon Avenue is littered with broken pieces of pavement after a water main break overnight flooded the Studio City neighborhood and created a large sinkhole under the street, which then collapsed. Credit: Irfan Khan / Los Angeles Times

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Comments () | Archives (8)

Close inspection of each failed pipe should provide the evidence of the failure mode. Evidence of corrosion would differ from evidence of a tear or shear in the pipe due to an external force such as ground movement. These evidences haven't been reported yet, AFAIK.

"putting added stress on already aging pipes." How OLD are these pipes anyway? - maybe it is just time - Bridges should be a concern as well.

Why are they considering using Cornell University, rather than the Cal State University System, or the UC campus system for assistance in this study? Are California geology professors somehow less knowledgeable about earthquakes than the good folks at Cornell? Somehow, I doubt it.

Has anyone considered the obvious? All this started happening when water-use restrictions were implemented. The likely explanation is that the system can't handle the added intermittent pressure caused by the water not flowing through at a regular pace. These "explanations" of why the blowouts are happening sound like typical bureaucratic fingerpointing to avoid responsibility.

Oh, great... Just what we need, the big one coming soon.

And why is David Nahi being paid 80 grand for consulting fees?

Ground movement was the first thing I suspected. We've had water rationing before and never had this problem. Is there perhaps something someone isn't telling us so as to not create a panic?

Well, this article was written on October 9th and now as of December 10th...we still have no answer about this "investigation"? Go to www.cbs2.com and type "earthquakes" and "water mains" into the search engine. The connection is obvious. Scroll back to early September on both. Also, just for fun, go to www.usgs.gov and click on earthquakes link and look at the faultline. WHEN will the news come clean and dig a little deeper into this issue and do FAR MORE about earthquake preparedness? And if the water mains are creating sinkholes and geysers now, imagine an 8.0 quake? The ground would be flooded and saturated (and sinking) with the entire system blowing, sinkholes would be rampant, PUMPS would be broken and LA would effectively be without water...for potentially months, creating mayhem and a mass exodus. It is time for news that run deeper than the latest thrill of watching a golf pro's life go down the drain. Who cares? That is followed up on DAILY...but this takes over TWO months??? KIDS live in LA, and deserve to be protected. Everyone does. Please LA Times, give educated news so people can make educated decisions about their safety. By the way, WHERE is David Nahi living now? Did he bail out of LA, or CA altogether?


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