The Safety of the Nation's Highway Bridges
LIANE HANSEN, host:
This is WEEKEND EDITION from NPR News. I'm Liane Hansen.
This month on our program, we are examining the nation's crumbling infrastructure. One of the most vivid examples of that happened last summer when a bridge span on I-35W collapsed in Minneapolis. Thirteen people died and hundreds were injured after dozens of vehicles plunged into the Mississippi River.
Unidentified Man #1: And we have a breaking story to pass on to you. There has a major bridge collapse in Minneapolis on one of the most...
Unidentified Woman: It's, like, I screamed, oh my God, call 911. I...
Unidentified Man #2: The bridge broke right behind my front tire and my pickup fell down probably around ten or fifteen feet onto the concrete below.
Unidentified Man #3: One of the guys that ran down there to see what happened and then he came back. I asked him what happened; he told me that the bridge had collapsed.
HANSEN: The Minnesota Department of Transportation, or Mn/DOT, is racing to rebuild the bridge, and the National Transportation Safety Board is still investigating the cause of the collapse. But in the meantime, motorists in Minnesota have learned to cross their fingers when crossing a bridge.
The state recently closed another major bridge and limited traffic on two others because of safety concerns.
Minnesota Public Radio's Sea Stachura reports.
SEA STACHURA: At the moment, the new I-35W Bridge across the Mississippi consists of two halves, jutting into the Mississippi and leaning toward the other. I stand on a catwalk along the edge of one half and look down. The river frosts around barges loaded with construction equipment, as Mn/DOT's Kevin Gutknecht points to the barges.
Mr. KEVIN GUTKNECHT (Mn/DOT): Now, if you look in the barge in the back you see there's a segment sitting there, and that segment has a bracket on the top. What happens when they are installing is the crane will reach over and pick up that segment and lift it up to the bridge and install it in place. You see where these - they may be getting ready to do one over here eventually. They stopped because of the rain and the lightning.
STACHURA: We climb down a ladder, through some rebar and into the girder of the bridge. It's like a concrete tunnel with a city of men. Gutknecht pauses beneath some cantilevers. Above us is the bridge deck. Gutknecht says the bridge is partly held together by a series of suspension cables that run through the cantilevers.
Mr. GUTKNECHT: So, the cables come through that conduit, they get strung through this anchor. There are little collars that fit around each cable; they're cone-shaped, and this is cone-shaped as well. So, when you run them through, you put the cone-shaped anchor on the wire, you pull it back into the anchor. The harder you pull on the cable, the tighter the grip becomes on the cable and that's how it gets held in place in this anchor.
STACHURA: Millions of pounds of pressure will pull on these collars. Guttnick finds one on the ground and hands it to me. The inside feels like sandpaper.
While the public wasn't involved in the bridge design, public meetings were held to gather input, and every week Gutknecht gives a talk about the bridge. More than 300 construction workers crawl around this beast 24 hours a day, six days a week. It's expected the bridge will cost the state at least $255 million and be completed by September.
But you can't help looking at this bridge without thinking about the other. Though Kevin Guttnick says the two bridges are nothing alike.
Mr. GUTKNECHT: You know, it's difficult to compare the two bridges except for where they're located. You know, they're both located in the same place. This is a concrete box girder bridge; that was a steel truss bridge. This was a redundant design. That was a fracture-critical design.
STACHURA: In an unusual twist, the design and construction companies are completely liable for the bridge. Mn/DOT project manager Jon Chiglo says each time a feature of the bridge is adjusted, the designer checks it against the original plans to ensure the bridge's integrity.
Mr. JON CHIGLO (Project Manager, Mn/DOT): That engineer record review and working with the foremen is the first line of the inspection. There's two other levels of inspection and testing that occur for the materials and workmanship and the placement of the steel and the different elements of this structure before it even gets to Mn/DOT. So, there is three lines of inspection that occur before Mn/DOT inspects it.
STACHURA: That approach is being carried out as two critical reports find that Mn/DOT engineers and inspectors didn't communicate about the condition of the Minneapolis bridge. Its inspectors failed to document an obviously bowed gusset plate. A legislative report completed by a local law firm found costs influenced maintenance decisions.
Lead investigator Bob Stein says Mn/DOT officials claimed money did not affect safety decisions.
Mr. ROBERT STEIN (Lead Investigator): What the record seems to document, however, memos that we went through and the various interviews that we had, that in a slow process of deterioration of a bridge, many decisions have to be made along the way and funding considerations enter into those decisions as to whether or not to elect one option or another option to proceed. And so we believe that, yes, funding did influence decisions along the way.
STACHURA: Now, while the state builds one bridge it has had to close some others. The one now featured on the Post Office's commemorative Minnesota stamp was closed just last week due to corroded and bowed gusset plates. The bridge is now open to limited traffic. A major bridge in St. Cloud was closed two months ago for similar reasons. That bridge is being replaced. And officials limited traffic on a third interstate bridge in Duluth.
Mn/DOT state bridge engineer Dan Dorgan says his inspectors are just being conservative in light of a tragedy.
Mr. DAN DORGAN (State Bridge Engineer, Mn/DOT): When we see problems, we take what action we think is the right action. And while does it generate a lot of publicity, it generates a lot of questions, I guess our expectation is we just have to handle those. We just have to be confident in ourselves that we've done the right thing.
STACHURA: That's why a bridge that will be built in record time will be checked, checked again and then checked one more time.
For NPR News, I'm Sea Stachura in Minneapolis.
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