CHICAGO (CBS) -- A stretch of northbound Lake Shore Drive is still shut down hours after a city crew, fixing streetlights, spotted a giant crack on a beam right under Lake Shore Drive.
The Chicago Department of Transportation said there's just the one crack, but right behind it, CBS 2 found another cracked beam. Motorists would have no idea it was there.
CDOT quickly shut down the northbound lanes between Monroe and Grand and dispatched crews who gathered beneath the massive bridge to survey the damage.
In a statement CDOT said, "Crews are working to install a shoring tower as quickly as possible under the viaduct structure that carries northbound Lake Shore Drive."
CDOT says the road will be closed through Monday's evening rush hour and possibly longer.
Patrick McBriarty, an author of books on Chicago's many bridges, happened to be trapped at the nearby yacht club and came to have a look.
"I was actually stuck in the traffic coming up Lake Shore Drive and then saw the notification in the email about that there was some kind of an emergency on the bridge," he said.
"When you see a crack that bad it makes you wonder about the city of Chicago and what they're doing to fix it, and if you go on other roads you feel unsafe, too," said driver Vicki Seshardri.
In addition to the northbound lane closures, on ramps at northbound Randolph and Monroe were also closed, leaving tens of thousands of cars driving through detours.
And the resulting gridlock left traffic funneling onto Columbus heading north or using Lower Wacker to get around emergency crews working on Lake Shore Drive.
This bridge was last inspected in June of 2017. It is supposed to be inspected every two years.
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