Restoring Drinking Water After Hurricane Helene | Oyster Shell Reefs And Sea Level Rise

Fifty-three days after Hurricane Helene, residents of Asheville can safely drink their tap water without boiling it. Why did it take so long? And, tribes’ historic lands on the Gulf Coast are being lost to the sea. To slow it down, one tribe has turned to oyster shells.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:03Speaker 00

  How can oyster shells be used to fight climate change?

• 0:06Speaker 01

  You could really see how the reef is slowing down the water. Like, there's waves on one side, but the water between the oyster reef and the mound was almost completely still.

• 0:15Speaker 00

  It's Tuesday, November 26, and you're listening to Science Friday.

• 0:22Speaker 00

  I'm Sci-Fry producer Dee Peterschmidt. Later in the episode, we're going to find out why a coastal tribe near New Orleans is building oyster reefs to lessen the effects of rising sea levels in their community. But first, we're going to check in on Asheville, North Carolina, which was only able to restore clean drinking water 53 days after Hurricane Helene. Why did it take so long? And what can other cities do to protect their drinking water supply after a massive storm? Here's Sci-Fry guest host Kathleen Davis.

• 0:49Speaker 02

  When Hurricane Helene barreled through the southeast US in September, it dumped an estimated 40 trillion gallons of water onto the region. That resulted in immense flooding, which destroyed roads, buildings, power lines, and other infrastructure. And it also impacted the region's potable water supply. For weeks, residents in Asheville didn't have access to drinking water, which comes from a local reservoir. And we actually heard from two listeners based in Asheville who had some questions about why this purification process can take so long.

• 1:24Speaker 03

  Hi, Science Friday. This is Sarah.

• 1:27Speaker 04

  And Allison.

• 1:27Speaker 03

  From Asheville, North Carolina.

• 1:29Speaker 04

  Unfortunately, the storm destroyed all of the main distribution lines coming from our reservoir, leaving the entire city without running water for weeks. But now that those lines are mainly functional, the reservoir turbidity levels are so high that they cannot run the sediment-filled water through our treatment plant.

• 1:48Speaker 03

  We'd like to know more about the science behind the turbidity issue and why, even though it has been dry for weeks after the storm, the sediment won't settle. It feels like this is an intersection of geology, chemistry, even physics, the impacts our everyday lives. So we might as well be curious and learn from it.

• 2:06Speaker 04

  We love the show so much. Thank you. And also, we'd like to say thanks to all the Water Resource Department employees and outside helpers that have been working tirelessly on this issue on behalf of the city of Asheville.

• 2:20Speaker 02

  That was recorded shortly before limited potable water access was restored earlier this week, marking the first time in 53 days that its residents didn't have to boil tap water. So why can it take so long for cities to clean their potable water after a storm like this? And what could other regions expect from the aftermath of future extreme weather? Here to tell us more is my guest, Dr. Sarah Ledford, Associate Professor of Geosciences at Georgia State University, based in Atlanta, Georgia. She studies the role and impact of water in urban areas. Dr. Ledford, welcome to Science Friday.

• 2:57Speaker 05

  Thank you so much for having me.

• 2:59Speaker 02

  So can you sum up for listeners, what's happened to Asheville's water and the region since Hurricane Helene?

• 3:06Speaker 05

  Yes, absolutely. I think there's really been three steps in the process after waters receded. The first is the rebuilding of any infrastructure that was washed out. So if pipes were washed away, those had to be rebuilt. We had to get power back up to the water treatment plant. The second problem is exactly what the callers were talking about, which was the unprecedented volume of water that came in washed huge amounts of sediment into the reservoir. And in the mountains of North Carolina, that includes a lot of clays. And clays take a long time to settle to the bottom, but we can't put that water through the drinking water process until those clays are removed.

• 3:49Speaker 05

  And so that's a lot of what the Asheville Water Department was working on, was trying to do what they could to speed up that process of clay settling. And then the final problem is that after the water is potable at the drinking water plant, the entire system has to be flushed so that we can make sure all pipes throughout the whole distribution network have clean and safe water.

• 4:11Speaker 02

  So it sounds to me like, you know, city treatment plants are set up to filter certain things, but maybe they're not set up to filter things that are unusual, like clay.

• 4:23Speaker 05

  Yeah, for many places, especially ones that pull water from a drinking water reservoir, that reservoir is sort of the assumed place where settling will happen. Other places that might pull water from a stream or river may actually have a tank in their system where they do settling. But when you have a reservoir that usually does this process very well for you, why would you build extra infrastructure that you don't typically need?

• 4:47Speaker 02

  Yeah. So our listeners mentioned that the water in the reservoir has a high turbidity level. I'm not very familiar with this concept. So what is high turbidity and what does it have to do with potable water?

• 5:00Speaker 05

  So high turbidity is basically a measure of how much light gets scattered by water. When you have water that is very clear, light that you put into that water can go on basically forever before it gets scattered or reflected back to the measurement device. When you have water that is full of sediment, especially clays, that light can't get very far before it reflects back to you. It looks cloudy to us as humans. And so high turbidity is used as a surrogate measure for high sediment in the water.

• 5:30Speaker 02

  So our listeners Sarah and Allison asked why the sediment in the water is negatively charged and flat shaped. How does that impact the purification process?

• 5:40Speaker 05

  Yeah, clays are a byproduct of a lot of long, long processes of weathering of rock. And clay minerals, which make up most of what we colloquially call clay, are what are called phyllosilicates. And these are a class of minerals that are formed in sheets. And so that's why the clay is flat, is that the way that all of the atoms are bonded together results in sheet-like formations. The other thing that clays have is they have a high static electricity on the outside of the clays because those oxygen atoms that are at the outside of those bonds result in those sheets of clay having a negative charge on the outside.

• 6:24Speaker 05

  And then when negative comes close to negative, or two clay particles come near each other, they're going to repel each other because they're both negative.

• 6:32Speaker 02

  So our next question is also from our listeners.

• 6:35Speaker 04

  They're using aluminum sulfate and caustic soda to try and bring the turbidity down. How do those chemicals interact with the sediment?

• 6:43Speaker 02

  So yeah, how do you even begin to clean this?

• 6:47Speaker 05

  So what they're using are actually techniques that are typically used at wastewater treatment plants because this is a process we do when we treat wastewater at the other end of the system. They're trying to get the sediment to form into flocks. And what that means are just larger particles. So the chemicals that they're adding are trying to overcome that negative repelling action and cause clay particles to start to stick together. And then the larger and larger the particle becomes, the easier it is for gravity to pull it to the bottom of the lake. And then they can pull the clean water from the top of the lake into the drinking water plant to be treated.

• 7:21Speaker 02

  Okay. So our most recent update from Asheville is that the water is safe to drink, but it's not totally clean yet. And city officials are recommending to not use large amounts of the water for landscaping and long showers. How long might it take for things to get completely normal?

• 7:38Speaker 05

  The good news is that if the city is saying it's safe to drink, that means that there's no bacteria or pathogens in the water. And as humans, that's really one of our biggest concerns about safe drinking water is we don't want anything that's going to make us sick in the water. From my reading, it sounds like the turbidity is still a little bit high, but it's coming down very quickly and much closer to the pre-heline conditions. And so I don't know that we really have a clock at this point because the city has said it's safe to drink. The other question, though, I think really has to do with the volume of water. And that's probably why they're encouraging folks not to water their lawns. They want to make sure that the water is being used for the most important purposes

• 8:20Speaker 05

  and for human consumption because it may still be waiting for other parts of the lake to have the turbidity come down. And we don't want to pull too much volume off the lake into the treatment plant.

• 8:30Speaker 02

  So after the hurricane, there was a lot of news around Asheville that it could no longer be considered a climate haven. We're going to continue to see more extreme weather events like this in the future. Can other regions expect this kind of problem with their drinking water if it's based in an open air reservoir that, you know, maybe they haven't experienced before?

• 8:53Speaker 05

  I think absolutely. I think what we know about climate change is that it's increasing the ability of the atmosphere to hold water vapor, which means extreme precipitation events are going to become more likely. The other compounding factor that we get in regards to drinking water reservoirs and climate change is wildfires.

• 9:12Speaker 02

  Hmm.

• 9:12Speaker 05

  One of the things that helps keep sediment from flowing off the environment into a drinking water reservoir is the vegetation that holds all of that material in place. I think another really big risk that we have coming forward is if areas that have had wildfires come through, get large rain events on them afterwards, that are areas that are source water for a drinking water reservoir, we're very likely to have a similar problem, potentially even with less rain.

• 9:38Speaker 02

  Is there a way for local governments to prepare for this?

• 9:42Speaker 05

  Continuing to try and make sure your source water area is protected, that it's not being developed, because that's going to be the best chance that we have for keeping vegetation in place. I think that's a really key piece of the puzzle. Another one is continuing to use controlled burns to mimic the natural wildfire patterns, which will then hopefully decrease the ability for a very extreme wildfire to come through and do as much damage, is another key piece.

• 10:12Speaker 02

  Hmm. So you study community engagement in urban water management. Do you have any thoughts about how residents of Asheville and other cities can get more involved in their water systems in this kind of context?

• 10:25Speaker 05

  Yeah, I always encourage everyone to try and do what they can to understand where the money that they pay in their bills is going. So you're paying a water in a sewer bill every month if you're getting drinking water from a centralized system like this. How is that money being distributed? I also encourage people to continue to try and understand the double whammy that many drinking water facilities are facing, which is the potential that they're going to have to treat new and more difficult chemicals, for example PFAS concerns, while also making up for the fact that across the United States, overall, we've under-invested in our infrastructure and we're having to play catch-up to repair it and get it back up to the best quality.

• 11:08Speaker 02

  Hmm. Well, that is all the time that we have for now. Thank you so much for explaining this to us.

• 11:14Speaker 05

  Thank you for having me.

• 11:15Speaker 02

  Dr. Sarah Ledford, Associate Professor of Geosciences at Georgia State University, based in Atlanta. And thank you to our listeners Sarah and Allison from Asheville, North Carolina for writing in. If you have a science question about an issue in your city, you can reach out to us at sci fry at sciencefriday.com. That's sci fry at sciencefriday.com.

• 11:40Speaker 00

  After the break, how recycled oyster shells from restaurants are helping a Gulf Coast tribe slow down sea level rise.

• 11:52Ira Flatow?

  Hey there, folks. Thanks for you being here. I just want to say how grateful I am for you. By listening to this podcast, you're making my work more fulfilling and sharing in my curiosity and love for science. You're also keeping the conversation going beyond just Fridays. Science Friday continues to make an impact because of people like you and your commitment to factual science news and information. Our work and this podcast depend on public support. And if every listener gave us just $2, Science Friday would be funded for the whole year. We know not everyone is in a position to give, but if you are, please make a donation to support

• 12:35Ira Flatow?

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• 12:48Speaker 07

  I'm Kevin Ruess. And I'm Casey Newton. And together, we've been tech journalists for decades. Now, we're your hosts of Machine Gods, a new podcast from NPR that makes sense of what AI means for your work, your life, and all of our futures. Twice a week, we'll be exploring the biggest moves in tech and give you unmatched access to the real titans of industry. Listen to Machine Gods from NPR on the NPR app or wherever you get your podcasts.

• 13:17Speaker 02

  It's time to check in on the state of science. This is KERA News. For WWNO. St. Louis Public Radio.

• 13:24Speaker 04

  Iowa Public Radio News.

• 13:26Speaker 02

  Local science stories of national significance. As we're seeing sea levels rise across the world, we're also seeing how communities close to the water are responding differently to it. In Louisiana's Grand Bayou Indian Village near New Orleans, tribes are witnessing their historic lands disappear underwater. And their solution, for now, is oysters. Here to tell us more is my guest, Eva Tesfai, coastal reporter at WWNO in New Orleans. Eva, welcome back to Science Friday.

• 13:58Speaker 01

  Thanks for having me.

• 13:59Speaker 02

  So can you tell us about what this tribe has been going through?

• 14:03Speaker 01

  Yeah, so like you said, Grand Bayou Indian Village, it's about an hour south of New Orleans. It's in Plaquemines Parish, along the Mississippi River. It's home to the Atakapa Ishak Shawasha tribe. It's a very small village. In the 40s, there was about 1,000 people living there, and now there's only about a dozen. They live in the marsh, and you can only get around by boat. So that means all the homes have been raised on stilts to help deal with hurricanes, and they've lost a lot of people. A lot of people have moved out, but they're also losing land. And that's obviously due to sea level rise, that's driven by climate change, and it's causing their land to disappear.

• 14:45Speaker 02

  And I've heard that this is getting so bad that GPS maps aren't even accurate anymore. Is that right?

• 14:52Speaker 01

  Yeah, one person I was talking to while I was down there says sometimes you'll be like looking at the GPS and you'll see land on the map, and then you just look up and it's all water.

• 15:01Speaker 02

  Oh, my gosh. So tell me how oysters play into all of this.

• 15:06Speaker 01

  Right, so this was a project between Grand Bayou and the Coalition to Protect Coastal Louisiana. Basically, the coalition brought a bunch of volunteers and a bunch of bags of recycled oyster shells, and they had the volunteers stack the shells all along the shoreline in front of people's houses. So... These shells will help slow the water and help protect that land from erosion. But it's also a living reef, so oysters will attach. It'll create this beautiful little ecosystem. And that means the reef will also grow as the sea level rises and continue providing that protection.

• 15:41Speaker 02

  And you were there. Was it easy to see the effect that these oysters were having?

• 15:47Speaker 01

  Yeah, so this was the second time the Coalition has done this kind of project with Grand Bayou. They actually chose to do this to protect one of their sacred mounds first. That's called the Lemon Tree Mound. So we went to go see how that reef was doing. It was installed about two years ago. And Richie Blink was the boat captain. He took us out there. He runs Delta Discovery Tours. He pointed out how the oysters and other critters are already attaching to the reef.

• 16:15Ira Flatow?

  So this is an oyster drill conch. So this is a predatory snail that actually eats oysters. So that's just telling us that there's, that there's oysters that are actually here. Yeah, fishermen don't like these very much.

• 16:27Speaker 01

  So there are all these snails and crabs and things attached to the reef. And what I also noticed is you could really see how the reef is slowing down the water. Like, there's waves on one side, but the water between the oyster reef and the mound was almost completely still.

• 16:42Speaker 02

  Wow. So I can imagine we're talking about a lot of oysters here, right? Where is the tribe getting them?

• 16:50Speaker 01

  Yeah, the reef they built to protect their homes was 900 feet long. So yeah, that's like thousands of oyster shells. And yeah, they get them from restaurants in New Orleans. The Coalition also just expanded to collecting from restaurants in Baton Rouge. So it's kind of a nice way to recycle these oyster shells and bring them back into the environment.

• 17:08Speaker 02

  So this starts with recycled oyster shells, but then it becomes a place for living oysters and other kinds of marine animals. At the same time, it makes flooding from storms less of an issue. But they can only help so much, I'm guessing. Is that a correct read on that?

• 17:25Speaker 01

  Yeah, I talked to Rosina Philippe. She's a tribal council member and the tribe's knowledge holder. And she talked about that. She basically said they know it won't be enough to stop the land from disappearing completely, especially for Lemon Tree Mound. It will eventually, you know, succumb to the waters and the waves, which is okay. But the reef that was created there will serve as not only a Marker of where that site was, but it it actually encourages marine life to congregate there and to repopulate the area. So basically, it's worth it anyway, because they're taking care of not only their land, but they're also taking care of the marine environment.

• 18:09Speaker 02

  Mm hmm. So what would this tribe do if their land disappears?

• 18:14Speaker 01

  Well, they're not going to leave. Philippe made that very clear to me that this is their home and they're going to stay no matter what. And like I said, they already raised their homes on stilts. They're also looking into floating houses and gardens and other adaptation methods. Philippe says they're historically a water people, like they would move to adapt to the water as it changed historically. So now they're just returning to that way of life and relearning how to live with water.

• 18:43Speaker 02

  Well, that's all the time that we have for now. I'd like to thank my guest Eva Tessfi, coastal desk reporter for WWNO in New Orleans. Thanks so much for joining us.

• 18:53Speaker 01

  Thank you.

• 18:56Speaker 02

  One last thing before we go. Are you thinking about getting books for the curious young minds in your life, but you need some suggestions? We're covering the best science books for kids from this year, and we want to know more about who you have plans to shop for this holiday season. Go to sciencefriday.com/kidsbooks to send us your requests, and we'll ask our experts for an upcoming story. That's sciencefriday.com/kidsbooks.

• 19:28Speaker 00

  And that's all the time we have for today. Lots of folks helped make the show happen, including

• 19:31Speaker 01

  Jordan Smudgic.

• 19:33Ira Flatow?

  Charles Burquist. Shishana Buxbaum.

• 19:35Speaker 00

  George Harper. Tomorrow, is seed oil bad for you? And what's the difference between processed and ultra-processed foods? We have a nutritionist to answer our listeners' questions about viral health claims. I'm Sci-Fri producer Dee Peterschmidt. Thanks for listening.