The main highway connecting California and Arizona, which has been closed east of Coachella since flash flooding damaged several bridges, will reopen to limited traffic Friday, transportation officials said.
The California Department of Transportation had expected the closure of the 10 Freeway near the town of Desert Center to last weeks, but officials said Tuesday that work was progressing fast enough that a limited reopening was possible sooner.
One lane of traffic in each direction will use what normally is the westbound span of the bridge over a small desert gully. That bridge was damaged but not broken by erosion caused by the flooding.
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The eastbound span, which buckled into the gully, will take longer to fix.
The flood damage that occurred over the weekend has proven 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 Caltrans 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 I-10, 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 detour of several hours.
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 had hoped to reopen the westbound lanes around the collapse site to two-way traffic within weeks, but Caltrans said it was able to enter into an emergency contract to get the work done quickly, and Granite Construction Inc. was awarded the project.
Once traffic returns to I-10 Friday, minor work will continue to be performed on the westbound side, and work will begin to reconstruct the eastbound span, Caltrans said.
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.