KELLY MCEVERS, HOST:
In northern California, the mandatory evacuation order for people living near the Oroville Dam has been lifted, so people can go home. But the local sheriff is warning people in the area that conditions could rapidly change, and they could require a new evacuation at any time.
The concern is over structural problems at the dam, and as we learned this week, environmental groups raised concerns about these problems more than a decade ago. But at the time California, and federal officials dismissed them. I talked about this with Paul Rogers. He's with member station KQED in the San Jose Mercury News. And I asked him about those warnings.
PAUL ROGERS, BYLINE: Well, in 2005 when the federal government was relicensing this dam, lots of people wrote comments and talked about it. And there were three environmental groups including the Sierra Club which said, you know, the emergency spillway here looks dangerous. It has a concrete lip across the top, but beyond that, if any water ever flowed over it in big rainstorms, it would just run down a hillside. There isn't any concrete there. And the hillside is covered with trees, and all that could erode really badly. And it might actually undercut the reservoir itself and cause a catastrophic release of water.
MCEVERS: So why was the dam built that way in the first place?
ROGERS: That's one of the mysteries right now that is going to come out over the next months and years as all this is investigated and congressional hearings and lawsuits and things like that happen. And it's important to remember that the area is still not out of the woods yet. There's a big storm coming in this week.
And so the water, which is now about 10 feet below the level because they've been frantically releasing water - that could go right back up over the top again of this emergency spillway and threaten the failure. But you know, 50 years ago, for some reason, they cut corners on this, and we were probably going to find out eventually.
MCEVERS: Why didn't state and federal authorities make the kind of upgrades to the dam that could have prevented this along the way?
ROGERS: You know, some of it I think is engineering hubris. I just dug up some documents yesterday in which the state Department of Water Resources here in California in 2006 wrote that this emergency spillway was, quote, "a safe and stable structure founded on solid bedrock that will not erode." Well, after running water over it for just a few hours, the erosion was so violent and severe that they evacuated 200,000 people. So...
MCEVERS: Yeah.
ROGERS: That was it. Also, it costs hundreds of millions of dollars to fix and anchor and improve dams. And I don't think anybody wanted to pay.
MCEVERS: Right, so - but now they're going to have to pay, and who is going to pay?
ROGERS: That's one of the great unknowns. This could cost, you know, $500 million or more to rebuild both spillways on this dam. I think already California is asking the federal government for help. Certainly the state and water users are going to pay some money, but some people out here are nervous because President Trump - you know, he didn't win California, and so some of our elected folks are a little nervous that he may not be that excited to go to bat for hundreds of millions of dollars to help fix this.
MCEVERS: So without federal funding to help, what would that mean?
ROGERS: That would mean that state taxpayers and probably water users in Silicon Valley and the Bay Area and Los Angeles and the Central Valley, the farms - they would all see increases in their water bills over the coming years to fix it. But it's got to be fixed. This is the tallest dam in the United States, and it's broken.
MCEVERS: Paul Rogers of member station KQED in San Francisco, thank you.
ROGERS: Thank you.
(SOUNDBITE OF DAN ROMER AND OSEI ESSED SONG, "SHOWDOWN") Transcript provided by NPR, Copyright NPR.