Tuesday, July 21, 2015

Flood damage to California bridges worse than suspected

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Flood damage to California bridges worse than suspected

LOS ANGELES (AP) — The damage to interstate highway bridges from flash flooding in Southern California's desert over the weekend proved more widespread than initially thought, with construction crews working Tuesday to reinforce spans over three gullies.


Flood damage to California bridges worse than suspected


Associated Press


LOS ANGELES (AP) — The damage to interstate highway bridges from flash flooding in Southern California's desert over the weekend proved more widespread than initially thought, with construction crews working Tuesday to reinforce spans over three gullies.
In light of the damage, some outside engineers warned that the California Department of Transportation may need to adopt tougher design and protection standards for highway bridges, particularly with abnormally heavy rains possible in the coming months because of the ocean-warming phenomenon known as El Nino.
Flooding touched off by unusually intense rainfall of nearly 7 inches Sunday washed away boulders and soil under an elevated portion of Interstate 10 near the town of Desert Center, about 50 miles from the Arizona state line, causing the collapse of the eastbound side of the bridge and severely weakening the westbound side.
One person was hospitalized with broken ribs, a shattered knee and lacerations to his liver, and the main highway between Los Angeles and Phoenix was severed, forcing 54,000 daily vehicles to take a several-hours detour.
After the collapse, Caltrans inspectors found erosion under two other I-10 bridges a few miles to the west, and workers labored to reinforce all three spans by pouring more concrete and replacing the protective boulders that were swept away, said Mike Beauchamp, a Caltrans deputy district director.
Authorities hope to reopen the westbound lanes around the collapse site to two-way traffic within weeks. Reconstruction of the fallen eastbound span will take longer.
Caltrans said it inspected 10 bridges over I-10 on Monday and expected to complete the remaining 34 on Tuesday.
The bridge that washed out was built in 1967 and easily passed a March safety inspection. It had been "armored" with boulders lining the gully that runs under the span. The gully is normally dry but can flood during the sudden and intense rainstorms that happen in the desert.
Caltrans said the span would have withstood the flooding if the water had barreled down the middle of the natural channel, but its path shifted, as can happen in the desert, concentrating its full force on the western bank. The soil in that area cannot absorb that much water quickly.
Armin W. Stuedlein, an engineering professor at Oregon State University who studies how structures such as bridges interact with soil, said that in the wake of the collapse, there may be "room for improvement" in bridge design and protection standards.
Caltrans had no immediate comment.
Stuedlein noted that this stretch of I-10 has several dozen similar bridges.
"Any one of those gullies on any given storm event could be the bad actor," he said.
Another engineer said he worries that the kind of flooding seen Sunday could increase in coming months because of El Nino. The periodic warming of the Pacific Ocean waters could bring heavier-than-normal rains to drought-stricken California.
"As the prospects for El Nino continue to grow, what happened a couple of days ago is probably going to recur," said Ziyad Duron, an engineering professor at Harvey Mudd College.
end quote from:
http://finance.yahoo.com/news/california-interstate-collapse-reverberates-2-states-074716384--finance.html#

Flood damage to California bridges worse than suspected



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