Engineers Report More U.S. Dams Deteriorating As part of a monthlong series on America's infrastructure, Weekend Edition takes a closer look at the nation's dams. Nearly 80,000 dams across the country help control floods, provide hydroelectric power and regulate the water supply. But the number of dams considered unsafe has jumped 33 percent in the past decade, according to a report card by the American Society of Civil Engineers. Guest Host Audie Cornish speaks with ASCE Deputy Executive Director Larry Roth.

Engineers Report More U.S. Dams Deteriorating

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This is WEEKEND EDITION from NPR News. I'm Audie Cornish.

This month on our program we're examining the state of America's infrastructure, and today we take a closer look at the nation's dams. Nearly 80,000 dams across the country help control floods, provide hydroelectric power and regulate our water supply. While the majority of them are in pretty good condition, the number of dams considered unsafe has jumped 33 percent in the last decade, and over the years the U.S. has had a fair number of dramatic moments with its dams.

Unidentified Woman #1: On Monday, state inspectors made their annual check of the Seven Devils Dam and found water seeping through the structure.

Unidentified Man #1: The man just said that the dam burst up the head of Buffalo Creek and wiped it out.

Unidentified Woman #2: You didn't hear water per se but the water was clear up to the windowsill so...

Unidentified Woman #3: By the time that me and my husband and my children got onto the hill, we looked back over the mountain; there was no houses. Everything was gone.

Unidentified Man #2: And the dam, as it collapsed, began to lift and carry and tumble these enormous pieces of concrete, some weighing tons.

Unidentified Man #3: You know, I mean, I was scared inside. But, you know, we were worried about the house but I worry more about the lives of the people. You know, you can always rebuild your house.

Unidentified Man #4: That fact is that these dams kill people.

CORNISH: The American Society of Civil Engineers issues a report card on aspects of the nation's infrastructure, and they say the U.S. gets a D for how it takes care of its dams.

Larry Roth is the deputy executive director of the American Society of Civil Engineers. Larry, thank you for coming in to speak with us.

Mr. LARRY ROTH (Deputy Executive Director, American Society of Civil Engineers): Thank you, Audie.

CORNISH: Now, your organization's last report card - and from what I saw, it was from 2005 - said that 3,500 dams across the U.S. were unsafe. Now, how many of them have actually failed or collapsed in some way?

Mr. ROTH: In the last several years, there's actually been about 70 or so dam incidents, including 29 dam failures.

CORNISH: Can you tell us specific instances that you remember?

Mr. ROTH: The most recent dam failure was the dam in Hawaii that failed and I believe killed seven people but also caused extensive environmental damage.

CORNISH: And is that an instance where there is a crack or seepage or - what can go wrong?

Mr. ROTH: Well, we have to remember that most of our dams were constructed at least 50 years ago and, like all our infrastructure, dams deteriorate. And we're not helping the problem because we're often deferring maintenance.

CORNISH: Now, how can you tell when a dam is unsafe?

Mr. ROTH: Usually the most critical problem for dams is an inadequate spillway, which is an emergency relief so that as water in the reservoir rises, it doesn't rise to the point where it overtops the dam. But the spillway has to be big enough; it has to be big enough to pass the water safely in order to protect the dam structure.

CORNISH: So, when the spillway isn't big enough, that's when you get damage to the dam itself?

Mr. ROTH: That's right. The water overflows and erodes the dam and causes, in this case, a catastrophic failure. Dams also need to be regularly inspected, though. Smaller dams are subject to having problems from burrowing animals, for example. And so dams should be regularly inspected visually and there's also a simple instrumentation that can be used to check dams that maybe have some problems that ought to be looked at very carefully.

CORNISH: So, that brings us to oversight and maintenance. And, you know, you usually think of maybe the Army Corps of Engineers dealing with dams but it turns out that 95 percent of dams that are out there in the country are actually controlled by states and local government. So, where does that leave their oversight and maintenance?

Mr. ROTH: Well, that's a very serious problem. It's not just state and local governments, but dams are owned by private individuals. They're owned by quasi-governmental organizations like irrigation districts. And for some dams we don't even know who the owners are. They've been essentially abandoned, they're orphan structures. And so there's not even an entity that is providing the inspection and the maintenance.

CORNISH: You mention that there were incidents of dam failure over the last few years but we do not often hear about it in the news, and I'm wondering if you think that makes people kind of complacent about the topic.

Mr. ROTH: Well, I think with all of our infrastructure we only talk about it, discuss it and worry about it in the aftermath of a failure. And we can point to a number of recent failures. The tragic I-35 bridge collapse in Minneapolis last summer and then two and a half years ago, the Hurricane Katrina wreaking havoc with the levees in New Orleans.

And of course, as those infrastructure failures fill the headlines for the next several weeks, the nation's attention is focused on it. But as soon as those headlines go away, our infrastructure becomes, again, out of sight and out of mind.

CORNISH: Now, there's another report from the American Society of Civil Engineers scheduled for 2009. Can you give us a sense of if the situation's gotten any better or is getting any better?

Mr. ROTH: Unfortunately, I'd have to say no. There's been an opportunity for Congress to provide additional funding to help address the issues of deferred maintenance in our infrastructure, but even when we passed the highway bill in 2005, it was $90 billion short of what was really needed.

CORNISH: Larry Roth is the deputy executive director of the American Society of Civil Engineers. Larry, thank you for speaking with us.

Mr. ROTH: Thank you.

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