Inspecting a Los Angeles Bridge The I-35 bridge collapse in Minnesota has heightened concern about the more than 700 bridges that share the same design. There are two such spans in Los Angeles, and one crosses the Los Angeles river in the San Fernando Valley at Colfax Avenue.
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Inspecting a Los Angeles Bridge

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Inspecting a Los Angeles Bridge

Inspecting a Los Angeles Bridge

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MADELEINE BRAND, host:

Rainy weather is complicating recovery efforts at the site of a Minneapolis bridge that collapsed two weeks ago. Nine people are confirmed dead. Four others are still missing. Meanwhile, across the country there is concern about the more than 700 bridges that share the same design as the Minnesota Bridge.

JAMES HATTORI, host:

That design is called a steel-decked truss bridge. There are two of them in Los Angeles. One crosses the L.A. River and the San Fernando Valley at Colfax Avenue.

DAY TO DAY's Alex Chadwick met a city engineer there, veteran bridge man Clark W. Robins.

Mr. CLARK W. ROBINS (Deputy City Engineer, Los Angeles): The bridge is structurally sufficient. It's in good shape. You can see the paint is good. Steel bridges require painting periodically and they're maintenance intensive, and that's why we don't build many of them anymore, because we don't want to have to go back and paint them every 15 or 20 years. It's very expensive to paint this bridge. But you can see this one has been painted recently, and it's in good condition.

ALEX CHADWICK: I have read that these type of bridges used to be common. Back in the '60s, when they built that one in Minneapolis.

Mr. ROBINS: Right.

CHADWICK: Now they don't build so many of these. Is that because the design does not work or is it just the painting?

Mr. ROBINS: It's the maintenance cost of steel and the initial cost. Steel is more costly to construct initially now because concrete is plentiful. So you know, we use almost exclusively concrete in Los Angeles for those two reasons.

CHADWICK: When the accident happened in Minneapolis, I'm sure you got calls - your office got calls.

Mr. ROBINS: Oh, many. Yeah.

CHADWICK: People say, hey, come out and take a look at this. Did you come out and inspect this bridge?

Mr. ROBINS: Yes.

CHADWICK: Did you?

Mr. ROBINS: Yes, yes. I did not personally, but we certainly had it inspected. Yes, and it was found to be in excellent condition.

CHADWICK: And what does that mean when you inspect a bridge? What happens?

Mr. ROBINS: You notice things like this rust, for example. You look for any broken members or bent members or changed conditions from the last inspection. Has there been any damage from vehicles? You look at the foundations. You look at the - to see if there's been any settlement in the pier. You can tell that because you mark the pier where it intersects the river bottom and you watch to see if that changes. So we monitor every aspect of the bridge.

CHADWICK: Have you read and heard those reports, which surprised me from an engineering perspective, that back when they were designing these bridges in the mid-'60s and building them, they weren't really considering traffic load?

Mr. ROBINS: Well, you have to remember, especially on a long-span bridge, the traffic load is almost insignificant compared to the total load. The dead weight of the bridge is really the main problem that you're solving.

CHADWICK: That's what you have to contend with?

Mr. ROBINS: Yeah. So you're adding a relatively small percentage to that for traffic load. Now, they couldn't foresee the heavy trucks that were coming. And so they're probably under-designed slightly, but I don't think it's relevant to the total design of the bridge. In particular, it's not a big number. It's a small number.

CHADWICK: When I'm sitting in a traffic jam on a bridge, all these other cars, and it's just going through my head, gosh, there's a lot of cars on this, the reality is that weight is...

Mr. ROBINS: Doesn't mean too much. Especially cars. Trucks, if you have trucks backed up one behind the other, it's a little more significant. But still, I mean you can see how heavy these steel members are.

CHADWICK: Yeah.

Mr. ROBIN: The dead weight of the bridge is by far the most significant.

CHADWICK: When something like this accident happens in Minneapolis, it turns attention to these bridges. You get called out to do re-inspections and everything. But for you, in your situation, maybe it's good at least to have people reminded that...

Mr. ROBIN: We love it. I hate to say it that way, but you know, we have a heck of a time getting adequate staff to inspect, terrible time in normal years. I don't think we're going to have that problem for a few years. It's like earthquakes. You know, earthquakes come unannounced and bridges - cracks form and things happen that scare people. And we need to go out and close the ones that are at risk and keep the ones open that are not at risk because you need the evacuation route and the hospital, you know, the emergency vehicles, that sort of thing.

CHADWICK: Yeah.

Mr. ROBINS: I don't know if that answers your question. I hope it does.

CHADWICK: Clark Robins, deputy city engineer of Los Angeles at the Colfax Bridge.

Mr. ROBINS: Colfax Bridge. Show you the rest of them if you want.

CHADWICK: Clark, thank you.

Mr. ROBINS: My pleasure.

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