MESA — Parts of a bridge being built as part of the Loop 202 freeway extension in Mesa collapsed Thursday, but there were no injuries, officials said.
A concrete girder designed to support the roadbed on the span being built over Power Road collapsed, causing several others to tumble in a "domino effect," said Jeanine L'Ecuyer, a spokeswoman for Gov. Janet Napolitano.
The collapse dropped one section of the partially built bridge dozens of feet to the ground.
The concrete beams support the roadbed, but the span was not completed when they fell, L'Ecuyer said. If one had failed on the finished span, a redundant design would have prevented any collapse, she said.
Bill Pederson, a spokesman for the Arizona Department of Transportation, said 11 concrete girders on the affected part of the bridge were installed on top of support piers about three weeks ago and nine fell on Thursday. The fixtures that would hold the beams in place had not yet been installed.
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"In any construction project there are certain times when it is most vulnerable," Pederson said. "Because the girders had just been set on top of the pier caps ... they were vulnerable, but once these types of bridges are built they are very, very strong, they have lots of redundancy."
Inspectors from all relevant state and federal safety agencies, as well as ADOT, will investigate the incident, L'Ecuyer said. The bridge was being built by Phoenix-based Pulice Construction.
Pederson said it was too early to determine what caused the girders to fall.
Napolitano ordered ADOT to inspect all the state's existing highway bridges last week after the deadly collapse of a span over the Mississippi River in Minneapolis.
The five steel-deck truss bridges of similar design in the state have already been inspected and no major problems were discovered, L'Ecuyer said.
The bridge under construction was not part of the inspection order.
Pederson said bridges similar to the one being built in Mesa are used across metropolitan Phoenix and have proven extremely strong and reliable.
"Arizonans can be confident that our bridges are safe and once they are built they're going to stay up," Pederson said.
