Minneapolis Bridge That Collapsed Rated "Structurally Deficient" in 1990

MINNEAPOLIS (AP) - Minnesota officials were warned as early as

1990 that the bridge that plummeted into the Mississippi River was

"structurally deficient," yet they relied on a strategy of

patchwork fixes and stepped-up inspections.

"We thought we had done all we could," state bridge engineer

Dan Dorgan told reporters not far from the mangled remains of the

span. "Obviously something went terribly wrong."

Questions about the cause of the collapse and whether it could

have been prevented arose Thursday as authorities shifted from

rescue efforts to a grim recovery operation, searching for bodies

that may be hidden beneath the river's swirling currents.

The official death count from Wednesday's rush-hour collapse

stood at four, with another 79 injuries. But police said the death

count would surely grow because bodies had been spotted in the

water and as many as 30 people were still reported missing.

In 1990, the federal government gave the I-35W bridge a rating

of "structurally deficient," citing significant corrosion in its

bearings. The bridge is one of 77,000 bridges in that category

nationwide, 1,160 in Minnesota alone.

The designation means some portions of the bridge needed to be

scheduled for repair or replacement, and it was on a schedule for

inspection every two years.

Dorgan said the bearings could not have been repaired without

jacking up the entire deck of the bridge. Because the bearings were

not sliding, inspectors concluded the corrosion was not a major

issue.

During the 1990s, later inspections found fatigue cracks and

corrosion in the steel around the bridge's joints. Those problems

were repaired. Starting in 1993, the state said, the bridge was

inspected annually instead of every other year.

A 2005 federal inspection also rated the bridge structurally

deficient, giving it a 50 on scale of 100 for structural stability.

White House press secretary Tony Snow said while the inspection

didn't indicate the bridge was at risk of failing, "If an

inspection report identifies deficiencies, the state is responsible

for taking corrective actions."

Gov. Tim Pawlenty responded Thursday by ordering an immediate

inspection of all bridges in the state with similar designs, but

said the state was never warned that the bridge needed to be closed

or immediately repaired.

"There was a view that the bridge was ultimately and eventually

going to need to be replaced," he said. "But it appears from the

information that we have available that a timeline for that was not

immediate or imminent, but more in the future."

Federal officials alerted states to immediately inspect all

bridges similar to the one that collapsed.

The eight-lane Interstate 35W bridge was Minnesota's busiest

bridge, carrying 141,000 vehicles a day. It was in the midst of

mostly repaving repairs when it buckled during the evening rush

hour. Dozens of cars plummeted more than 60 feet into the

Mississippi River, some falling on top one of another. A school bus

sat on the angled concrete.

Engineers wondered whether heavy traffic might have contributed

to the collapse. Studies of the bridge have raised concern about

cracks caused by metal fatigue.

"I think everybody is looking at fatigue right now, fatigue due

to heavy traffic," said Kent Harries, an assistant professor of

civil and environmental engineering in the University of

Pittsburgh's School of Engineering. "This is an interstate bridge

that sees a lot of truck traffic."

After a study raised concern about cracks, the state was given

two alternatives: Add steel plates to reinforce critical parts or

conduct a thorough inspection of certain areas to see if there were

additional cracks. They chose the inspection route, beginning that

examination in May.

Dorgan said officials considered the cracks on parts of the

bridge to be stable and not expanding.

When conducting inspections, Dorgan said, inspectors get within

an arm's length of various components of a bridge. If they spot

cracks, that leads to more hands-on testing to determine the depth

and extent of the fissures.

The collapsed bridge's last full inspection was completed June

15, 2006. The report shows previous inspectors' notations of

fatigue cracks in the spans approaching the river, including one 4

feet long that was reinforced with bolted plates. A 1993 entry

noted 3,000 feet of cracks in the surface of the bridge; they were

later sealed.

That inspection and one a year earlier raised no immediate

concerns about the bridge, which wasn't a candidate for replacement

until 2020.

In a 2001 report from the University of Minnesota's Department

of Civil Engineering, inspectors found some girders had become

distorted. Engineers also saw evidence of fatigue on trusses and

said the bridge might collapse if part of the truss gave way under

the eight-lane freeway.

"A bridge of that vintage you always have to be concerned about

that," said Richard Sause, director of the Advanced Technology for

Large Structural Systems Center at Lehigh University. "In a steel

bridge of that age, sure you'd be concerned about those kind of

things and be diligent about looking after it. And it seems like

they were."

It takes time for a fatigue crack to develop, but a crack can

then expand rapidly to become a fracture, said James Garrett,

co-director of the Center for Sensed Critical Infrastructure

Research at Carnegie Mellon University. "If you get a crack that

goes undetected it would be something that appears to happen more

rapidly."

At the scene, about 15 divers and a dozen boats were in the

water, but the search was proceeding slowly because of strong

currents and low visibility. By mid-afternoon, they had located

four submerged cars besides the dozen or so visible from the

surface.

"We have a number of vehicles that are underneath big pieces of

concrete, and we do know we have some people in those vehicles,"

Police Chief Tim Dolan said. "We know we do have more casualties

at the scene."

Meanwhile, relatives who couldn't find their loved ones at

hospitals gathered in a hotel ballroom for any news, hoping for the

best.

Ronald Engebretsen, 57, was searching for his wife, Sherry. His

daughter last heard from her when she left work Wednesday in

downtown Minneapolis. Her cell phone has picked up with voice mail

ever since.

"We are left with the hope that there is a Jane Doe in a

hospital somewhere that's her." Sherry Engebretsen was later

confirmed as one of the dead.

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Associated Press writers Seth Borenstein, Martiga Lohn, Ryan

Foley and Jon Krawczynski contributed to this report.

(Copyright 2007 by The Associated Press. All Rights Reserved.)

By SHARON COHEN and BRIAN BAKST

Associated Press Writers