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(AP)- Three weeks before the Interstate 35W bridge
collapsed, engineers and maintenance crews had their hands full
with a "pretty good size" hole that developed near one of the
concrete piers supporting the southern end of the bridge.
 


     E-mails obtained by The Associated Press show Minnesota
Department of Transportation officials puzzling over the source of
the hole, with one engineer suggesting it was part of a larger
erosion problem in that area. None of the e-mails reflect concern
that it would affect the structural integrity of the bridge.
   
   On Monday, state transportation department spokesman Kevin
Gutknecht downplayed the deformity, labeling it a washout instead
of a sinkhole, as several of the July e-mails call it. Gutknecht
said it was caused by water draining off the bridge.

      "It did not appear to have any impact on that particular pier.
That pier did not move," Gutknecht said. "In fact, it did not
move during the bridge collapse."

      Engineering experts said in interviews with AP that the hole was
worth studying, but they considered it unlikely to have caused the
collapse.

      But the documents, which include several e-mails and four
photos, have apparently been turned over to investigative teams,
according to an e-mail that made the rounds a few days after the
Aug. 1 collapse that killed 13 people. AP obtained the
correspondence through a freedom of information request.

      In a July 12 e-mail, Tom Osthoff, a maintenance supervisor at
the department, said, "I went and checked the sink hole out, it is
pretty good size." He said he had his crew put a barrier around it
so no one would fall in.

      The photos show a hole above and to the left of the support
pier. A paved downslope leading to the pier also shows signs of
slumping. The hole was estimated to be 4-feet-by-6-feet in diameter
and a couple of feet deep, Gutknecht said.

      "The pictures of the slope paving seem to suggest that the sink
hole is connected with ongoing subsidence of the slope paving,"
wrote Bruce Irish in a July 11 e-mail.

      Gutknecht said Monday that the hole was first discovered in
December and some initial repairs were made in January. Cold
weather hampered the work so crews put off additional repairs until
July. Forty-five wheelbarrows of moist concrete had been poured
into the hole, with work done as recently as July 25. The fix
wasn't complete by the time of the collapse.

      National Transportation Safety Board spokesman Terry Williams
wouldn't comment on the hole's place in the investigation.

      The area where the hole was found is where the bridge deck broke
away on the southern side. Crews spray-painted the word "keep" on
a steel beam from that section, presumably so investigators can
give it a closer look later.

      A month after the busy bridge plunged into the Mississippi
River, federal investigators have offered a few hints on where
their probe is headed, but no firm conclusions about what led to
the failure. A firm retained by the state to do a parallel
investigation has been silent about its findings.

      The NTSB has issued an alert about the gusset plates that tie
steel beams together, taken note of the heavy construction
equipment on the bridge at the time and raised questions about its
automatic de-icing system.

      The e-mails reviewed by the AP are the first mention of a hole
near any support piers. The piers are the concrete pedestals that
hold up the steel components of the bridge's underbelly.

      The department finished its last bridge inspection report in
June 2006, and did not mention erosion problems near the piers.
Officials have said they began a new round of inspections in May.
No reports have been made public from those latest inspections.

      On July 17, a week after Osthoff's initial message, he shared
with colleagues an appraisal by Dale Dombrowske, a bridge
maintenance supervisor.

      "He feels that there was a problem with the bridge that caused
this sink hole (wash out). At this point I would have to agree with
him, there does not appear to (be) any drain pipes in this
vicinity," Osthoff wrote.

      Along the way, state engineers checked in with their peers in
the city of Minneapolis to determine if the hole could be related
to underground sewer lines. J. Rich Profaizer, an operations
manager with the city, quickly replied that it was not. In a phone
interview, Profaizer said there were no sewer or storm drains
adjacent to the hole.

      Bashar Qubain, president and chief engineer of Wayne, Pa.-based
GeoStructures, has done geological analysis for transportation
projects in Pennsylvania, New Jersey and Delaware. At AP's request,
he reviewed the rock makeup detailed in the original I-35W bridge
designs.

      He said the limestone and dolomite are prone to caverns and
other underground erosion, and they tend to be part of a network
rather than a solitary deformity.

      "If there is a serious sinkhole happening on the surface there
is usually a deeper problem below," Qubain said. But, he noted,
the designs called for the piers to be built on solid rock,
diminishing the chances a sinkhole would jeopardize the bridge.

      Kent Harries, an assistant professor of civil and environmental
engineering in the University of Pittsburgh's School of
Engineering, also had doubts about the hole's contribution to the
collapse.

      He said that washouts and sinkholes - even deep ones - are
relatively minor compared to the size of the bridge's footings.

      "Assuming it's a relatively surface sinkhole, it probably
didn't have anything to do with it," he said, adding, "Like
anything else in a case like this, you can't discount anything."


Gallery

Disasters

E-mails obtained by The Associated Press show Minnesota
Department of Transportation officials puzzling over the source of
the hole, with one engineer suggesting it was part of a larger
erosion problem in that area.

Crews worked to fill hole near support before Minn. bridge fell

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