Iowa Bridge Inspectors Look for Damage as Flood Waters Recede

June 23, 2008

The floodwaters that have surged across much of Iowa this month have inspectors looking for damage to the state’s already troubled bridge network.

The flooding concerns come after a study earlier this year ranked Iowa bridges fourth worst in the nation.

The study by Washington-based industry and insurance group TRIP showed that 21 percent of the state’s bridges, or more than 5,100 bridges, were structurally deficient with major deterioration to decks or other major components. The label doesn’t necessarily mean a bridge isn’t safe, but it indicates potential problems.

Now, inspectors are busy making sure bridges haven’t suffered damage in the record floods that swamped much of Iowa’s eastern half.

Engineers and transportation officials said motorists should feel safe that if a bridge is open, it has been deemed safe for travel. But they acknowledged that little money is available if serious problems are found.

“If it’s just getting rock back in there, it won’t be too bad, but if there are structural problems that need to be fixed, it will stretch resources,” said Larry Roehl, the county engineer in Louisa County, where the flooded Iowa River has closed bridges at Wapello and Oakville.

If structural problems are found, costs for either bridge could soar to $1 million or more, Roehl said.

“Either one of those could put us in a tough situation,” he said.

In Oakville, the problem was further complicated by a cabin that was swept up in the flood water and became stuck under the bridge.

Such obstacles increase the risk of erosion of the riverbed around the piers, a process called scouring.

“What it does is, it obstructs the flow, and the velocity of the water increases and it increases the chance of scouring,” Roehl said. “When we have a high water event, we go out and do extra inspections to make sure there aren’t any problems.”

In Linn County, two historic trestle bridges shifted in the high water and will need to be lifted back into place, said county Engineer Steve Gannon. One of the bridges leads into the Indian Creek Nature Center. The other is in Bertram.

An inspection of about 70 of the county’s bridges has found no structural problems, he said.

Gannon said crews are finding some erosion under bridge approaches and on county roads that were covered by water.

“Most people think if the bridge is there, it’s fine,” he said. “Most problems happen when you run into a scour hole at the end.

“We’re breaking those down and filling those up already,” Gannon said.

He said motorists should remain cautious because the county can’t post signs everywhere.

In Cedar Rapids, the sight of bridges underwater was unnerving, but residents said they would feel confident using the bridges if officials deemed them safe.

“I’m always concerned that they’re structurally sound,” said 47-year-old William McMahon of Cedar Rapids. “When you see the water go over them it makes you wonder about their stability, but as long as they inspect them I’ll feel OK.”

Marci Heil, 39, of Cedar Rapids, said if the government said the bridges were safe, she wouldn’t give it a second thought.

“I think they’re inspecting everything very closely these days and I don’t think they would let us on them if they weren’t safe,” she said.

Dena Gray-Fisher, a spokeswoman for the Iowa Department of Transportation, said crews will closely inspect bridges as the water falls.

They will remove debris from under the bridges affected by flooding, then be lowered in a bucket over the side to do a “hands-on, arms-length inspection, looking at the critical elements of the structure, take a measurement and look for shifting, look for scouring,” Gray-Fisher said.

So far, few serious problems have been found, she said.

One exception was the Iowa Highway 24 bridge over the Turkey River in Fort Atkinson in Winneshiek County.

Part of that bridge collapsed early in the floods, causing it to divert water to the approach, which was washed away, Gray-Fisher said.

She said if any problems are found, a bridge wouldn’t reopen.

“The public should feel very safe that the bridge is OK if the road is opened back up,” Gray-Fisher said.

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