Of California's 23,000 bridges, 13 percent of them have been labeled structurally deficient, which has some Bay Area residents wondering if Wednesday's bridge collapse in Minneapolis could happen here.
Caltrans Director Will Kemptson said sometimes small things, like peeling paint, can be enough to get a bridge on the deficient list.
"So, it's not always a structural issue which gets the bridge on the list," Kemptson said.
The spokeswoman for the Golden Gate Bridge District said she does not anticipate the same problem happening here.
Marry Curry said Bay Area bridges are constantly being re-engineered because residents live in earthquake country.
She said the Golden Gate Bridge is built to move not only from an earthquake, but from heavy winds that blow through the Golden Gate.
Curry said bridge engineers will examine what happened in Minneapolis and learn from it.
MSNBC spoke to a civil engineering professor at San Francisco State who cited a report of fatigue in an earlier I-35 bridge federal report.
Elahe Enssani said she thinks the fact that a freight train runs under the I-35 bridge may have played a role in the collapse. Enssani said the trains could have caused the fatigue and also caused cracking.
There is a freight train under a portion of the collapsed section of the bridge, but it is not clear whether it was actually moving under the bridge at the time of the collapse.
Mark Ashley is a civil engineer specializing in bridge design who works for T.Y. Lin International in Southern California.
He told NBC11's sister station in San Diego there are a number of things that may have caused the bridge to collapse.
"It's a catastrophic bridge failure. It's shocking because it's so unusual... so rare," said Ashley.
"You can't rule anything out," he said.
Not even the Mississippi River.
Ashley pointed to a photograph of the collapse area he obtained from "Google Earth."
It shows water moving rapidly underneath the bridge. Ashley said fast-moving water can erode a riverbed and ultimately affect the stability of a bridge.
NBC11's Noelle Walker Remembers Bridge She Knows Well
I've called the phone numbers several times, and all I get is a fast busy signal. It's not that I think my friends and former co-workers were on the bridge that collapsed in Minneapolis yesterday; it's that I need to know they weren't.
I've seen the pictures on TV, and I can't believe my eyes. How did an entire bridge fall into the Mississippi River? I looked at that bridge every day for four and a half years. I lived in a loft overlooking the mighty Mississippi, jogged and biked under that bridge, and drove over it countless times. I can't believe it's gone.
The station I worked for in Minneapolis sent me to New York days after the 9-11 attacks. I spent 10 gut-wrenching days at "ground zero." I couldn't believe my eyes then either, but I knew what caused it.
That there was no terrorist attack, no earthquake, no big event before that bridge collapsed without warning is unnerving. I am not someone who thinks about "what ifs" all that often, but I have to think there are people who cross bridges today from the Twin Cities to the Bay Area and wonder what if it happened here on this bridge. I'm going to keep calling those phone numbers until someone answers.
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