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(CBS) — Steel columns so rusted they appear to be hanging by a thread — that’s what 2 Investigator Pam Zekman found holding up some underpasses and bridges.

An expert says immediate action needs to be taken.

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Steel columns — full of rust and looking more like Swiss cheese than support beams — help hold up an underpass on Cermak, just east of Canal.

Fred Pierre frequently walks under it.

“Yes, it is dangerous, it might fall any time,” he says.

Every day, hundreds of cars drive through the underpass. Trains rumble overhead.

“Some of these columns are not even supporting the structure,” says Gongkang Fu, an Illinois Institute of Technology professor and structural engineer.

He inspected the underpass and rusted-out support colums and said: “They’re so bad they need to be immediately replaced — immediately.”

Several, critical support columns failed his inspection.

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“Without them the bridge can collapse,” he says.

CBS 2 and Prof. Fu found more problems at an under pass at 31st and Stewart.  Roof beams were visibly bent; they’re supposed to be holding the weight of the bridge.

And then there is the underpass down the line near 28th and Stewart.  It’s apparently in such bad shape that barricades have been put up to prevent traffic from driving through it.

“I would rate them to be the lowest in the country in terms of maintenance. Apparently there’s no maintenance at all,” he said.

Both Union Pacific and Norfolk Southern railroads share responsibility for maintaining the bridges. They say they’re inspected once or twice a year and are currently safe.

Union Pacific says even their columns with holes through them are cosmetic, more than structural, problems.

They say repairs are scheduled for Oct. 19.

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