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Why the Tex Wash Bridge Failed

The Ragsdale Bridge, which is made of wood, is older than the Tex Wash Bridge, but survived the same flood on the same wash. Photo credit: Jay Calderon/The Desert Sun

By Brett Kelman for The Desert Sun

Six months ago, an unremarkable bridge on a desolate stretch of desert highway collapsed, severing one of the most important roads in the nation. A flash flood toppled the eastbound portion of the Tex Wash Bridge, which carried Interstate 10 across a dry riverbed near Desert Center.

The collapse occurred on July 19, after nearly 7 inches of rain fell on the Chuckwalla Mountains south of the interstate, then flooded into the wash below. The storm was extremely rare and powerful, but its destructive force was magnified by critical flaws in the design of the bridge, according to an engineering expert’s new study of the bridge failure.

The Tex Wash Bridge was built in 1967, as the I-10 slowly grew across the country, crossing the dry, dusty desert between the Coachella Valley and the Arizona-California state line. Dozens of short bridges were built in that stretch, but the Tex Wash was wide and delta-like, so it demanded a longer, stronger bridge.

Instead, construction crews narrowed the wash, then built a short bridge with a shallow foundation. They also re-shaped the wash into a curve, which directed the full force of floods against the eastern base of the bridge.

Eventually, when the heavy rains finally came almost 50 years later, the pressure was too much. A flash flood pummeled the bridge’s foundation until the concrete cracked and the asphalt tumbled into the rushing water.

“This was not good engineering,” said Abolhassan Astaneh-Asl, a UC Berkeley engineering professor, who visited the Tex Wash Bridge site in December. “In good engineering, you work with nature, you don’t fight against it.”

“Because the flood will always win.”

For months, Abolhassan Astaneh has been studying the Tex Wash Bridge, seeking to explain its collapse in July.

Astaneh has turned his attention to the Tex Wash Bridge, which he studied with the help of Maryam Tabbakhha, another structural engineer at Berkeley. Together, they are preparing a research paper on the cause of the collapse, spotlighting four “fatal flaws” in the bridge design. The paper is expected to be made public later this month.

Read more at The Desert Sun

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