Why Potholes Are So Bad As Winter Turns To Spring

NPR's Ari Shapiro talks with Jonathan Gano, director of public works for Des Moines, Iowa, about why potholes are so bad at the end of winter and what can be done about them.

ARI SHAPIRO, HOST:

It's that time of year where some parts of the country are still buried in snow while others feel like spring. In other words, it's pothole season.

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UNIDENTIFIED REPORTER #1: You know, it is the talk of the town right now. It's also everybody's enemy on the road.

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UNIDENTIFIED REPORTER #2: And these are everywhere.

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UNIDENTIFIED REPORTER #3: Everyone is posting where they've claimed to drive over some of the worst potholes in the city.

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UNIDENTIFIED REPORTER #4: It's been like riding on the surface of the moon - so many craters and potholes.

SHAPIRO: To help explain why the problem is so bad this time of year, we've called Jonathan Gano, who is battling potholes in Des Moines, Iowa. He is the city's director of public works. Welcome to ALL THINGS CONSIDERED.

JONATHAN GANO: Thank you. Happy to be here.

SHAPIRO: I've seen people in Des Moines and other cities saying they have never seen potholes as bad as right now. Is this year actually worse than normal?

GANO: This year is quite a bit worse than normal.

SHAPIRO: Why?

GANO: We've had a pretty brutal winter here in the Upper Midwest. We moved from a mild winter in mid-January to an extreme winter by the end of February. It's been quite a lot of winter all the sudden.

SHAPIRO: And potholes are caused - you're the expert here. But it's - what? - water getting into a crack that freezes and expands and breaks up the concrete - something like that.

GANO: Yeah. There's 40 different causes for all the different varieties of potholes. But the basic...

SHAPIRO: Are there really 40 different causes of potholes?

GANO: (Laughter) There's all kinds of modes of failure for pavement. What's likely the most common one in many parts of the nation where you have a street that's got multiple layers on it - we have this in Des Moines, where it's an older concrete street that's been overlaid with two inches of asphalt. What happens is, over time, the concrete and the asphalt shrink and grow at different rates as we experience temperature extremes. And then water will get in those cracks that are formed by that movement, and then it freezes and can pop out the top two inches of that asphalt.

SHAPIRO: Do these different kinds of potholes all have names?

GANO: The one I just described is called a pop-out. The most common ones are slab breaks, corner, you know, de-cracking, pop-outs, frost heaving. There's a whole menu of different ways that a street will fail.

SHAPIRO: Are they all basically fixed the same way?

GANO: In the immediate term, they're all fixed the exact same way. The remedy for a winter pothole patching is what's called cold mix asphalt - is the only kind of repair material that's available in the wintertime. And it's really not the best tool for the job. Much better is what we can get during the summertime - the same kind of asphalt that roads are built out of. It's called hot mix asphalt, but it's not available and not even made in the winter months. So we use an admittedly suboptimal repair material that's basically oily, sticky gravel and sand mixture that's pretty solid but not completely set up. So we can stockpile it in the fall and have it available in January and February and March.

SHAPIRO: In the best-case scenario, when you fill a pothole, how long does that repair last?

GANO: If you can get good material and it's a good, nice, dry summer day, a pothole can stay patched for months or even years at times. In the wintertime, you can sometimes only get a couple days. If you get a couple weeks, you'd be doing pretty good.

SHAPIRO: Well, in this unusually bad year, paint me a picture of the worst pothole that you have seen in Des Moines this season.

GANO: You know, the worst pothole is the one that you hit going 40 miles an hour when you weren't expecting it.

SHAPIRO: (Laughter) Anyone - yeah.

GANO: There was a radio station in town. And earlier in the week, they were giving away a free alignment to the caller that correctly identified the pothole that they were describing. I guess they're all, you know, unique features.

SHAPIRO: (Laughter).

GANO: But just like parents have no favorites - you know, all their children are their favorite. All 2,000, 3,000 potholes that have showed up over the last couple weeks are my least favorite, and I wish to get rid of them.

SHAPIRO: (Laughter) Jonathan Gano, good luck with that mission

GANO: Sure thing. Thank you.

SHAPIRO: He's director of public works in Des Moines, Iowa.

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