SCOOP: There's A Dirt Shortage : Short Wave Mud and dirt have often been treated as waste products from excavation or dredging sites. But these days, coastal communities need massive amounts of mud and dirt to protect their shorelines from rising seas. This is leading to a dirt shortage, where the demand for it is higher than supply. NPR climate correspondent Lauren Sommer gives us the scoop — including why one federal agency that has dirt often disposes of it instead of reusing it for these projects.

SCOOP: There's A Dirt Shortage

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MADDIE SOFIA, HOST:

You're listening to SHORT WAVE from NPR.

EMILY KWONG, BYLINE: Hey, everybody. Emily Kwong here with NPR climate correspondent Lauren Sommer. Hey, Lauren.

LAUREN SOMMER, BYLINE: Hey there.

KWONG: So you have a scoop on a job opportunity?

SOMMER: Yeah. I do. It's a job in a growing field. It deals with a hot commodity.

KWONG: OK.

SOMMER: And, you know, there's some opportunity there. Yeah. I met someone with this job. His name is Pat Mapelli And he's a dirt broker.

KWONG: A what?

SOMMER: A dirt broker. But he's not a fan of that title, just to be clear.

PAT MAPELLI: I hate that name, I'm going to be honest with you. Dirt just has that negative connotation. You know, you got to go wash up, right?

KWONG: So dirt, that's what you got for us today?

SOMMER: Yeah. His actual title, though, is land use manager. He works for Graniterock, which is a construction materials company. But his job is really important because of climate change. And right now, he gets a lot of phone calls about dirt.

KWONG: OK. But from who, exactly? Like, who needs dirt so badly?

SOMMER: Well, where I met him is a good example of that. It was on the shores of San Francisco Bay in the East Bay. And it was on top of an earthen levee. So basically, a big pile of dirt that separates the water from the land. But it was in rough shape.

MAPELLI: It's very much lower than it should be right now and very much narrower than it should be right now.

KWONG: Yeah. That sounds bad. I mean, levees are what prevent flooding and protect people and homes.

SOMMER: Yeah. Exactly. So Pat helps get the dirt there to build up the levees. And this area needs a lot, around 100,000 dump trucks full.

KWONG: Whoa. That's a lot.

SOMMER: Yeah. So he finds the people who want to get rid of dirt, like construction projects that maybe are digging out an underground parking garage. And he connects them with restoration projects that need it. And there's more demand than he can handle right now because...

KWONG: Wow.

SOMMER: ...The oceans are rising with climate change. And coastal cities are scrambling to defend themselves, whether it's, you know, building levees or restoring marshes. And for that, they need dirt and mud.

(SOUNDBITE OF MUSIC)

KWONG: So today on the show, why climate change is making dirt and mud incredibly valuable and how an obscure federal policy is making it harder for coastal communities to get it as they prepare for rising seas. This is SHORT WAVE, the daily science podcast from NPR.

(SOUNDBITE OF MUSIC)

KWONG: OK. At SHORT WAVE, you know, Lauren, that we care a lot about using the correct scientific terminology. So in order to build up their defenses, you said that cities are looking for both dirt and mud. Are those basically the same thing?

SOMMER: Yes. I'm very glad you asked that. They're basically the same. As you probably guessed, dirt is what you dig up on land. And it's actually better for building things like levees. Mud is dirt plus water. So it's kind of the wet version of that. And, you know, another name for that is sediment. And that's important because a lot of places are working on restoring marshes right now.

KWONG: Oh, OK. Marshes, I think of them as those ecosystems between the land and the water. They're deceptively easy to get stuck in, I'll tell you that.

SOMMER: You sound like you speak from experience here.

KWONG: Well, it's not my fault. I mean, they have all these cool grasses and water birds and wildlife.

SOMMER: And they're muddy.

KWONG: And they're muddy. It's hard to resist, like, poking around.

SOMMER: Yes. And I was in a muddy one in San Francisco Bay, actually. It was full of birds that were stopping there kind of on their migration to the Arctic. And when the tide goes out, you know, the marsh gets exposed. So they can kind of feed on the plants and animals in the mud there. And I was with Letitia Grenier, who's a senior scientist at the San Francisco Estuary Institute. And she was pointing out what gets missed by some of us, which is that marshes are also protecting the shoreline.

LETITIA GRENIER: And these marshes are knocking down the waves. They're absorbing the water. And they're really helping create flood risk management along the shore, which is critical for many billions of dollars of infrastructure, as well as neighborhoods and other communities along the shoreline.

KWONG: So they're kind of the same as levees, then. These marshes are holding back the waves that could be causing flood problems.

SOMMER: Right. But a lot of marshes have disappeared as people have developed the shoreline. You know, more than 90% of San Francisco Bay's historical marshes are gone. And there's a push right now to restore them for both wildlife and for people and to protect against sea level rise.

KWONG: Yeah. Wow. Ninety percent is a lot. So how do you even go about restoring a marsh, exactly?

SOMMER: Well, you need mud because...

(LAUGHTER)

KWONG: OK.

SOMMER: ...You need to create an area that's right around the height of sea level so the plants can grow high enough, and they're not totally submerged all the time by the water.

KWONG: OK. So just get some mud.

SOMMER: Yeah. But even after that, you still need more mud. You need mud on mud because sea levels are rising. So - you know, the marsh that maybe you just restored, which works really well for today's conditions, in the future, the water is probably going to get too deep for it. And it will actually drown the plants. So marshes need a little bit more mud every day. And that's carried in by the water. As Letitia describes it, you know, the tide comes in twice a day. But right before it flows back out, there's kind of this moment that's really important.

GRENIER: So it stops. And the water's not moving for a second before it turns around and starts to flow out. And all the mud falls out of the water and lands on the marsh at that moment. And so it's that full tide going in and out of the marsh that lets them be resilient and grow with sea level rise by letting the mud fall out.

KWONG: I never really thought about that, how the tide carries in mud that it's depositing. So it's just a little bit of mud being deposited every day. And that helps build up the marshes over time.

SOMMER: Yeah. And that's what's really kind of special about marshes. You know, human-built infrastructure, you know, like a levee or a seawall, it's static, right? It is what it is. But marshes can grow higher to keep up with climate change. And that's why you need this kind of regular supply of mud. Letitia and her colleagues, you know, crunched the numbers and they found that San Francisco Bay will likely need more than 500 million metric tons of sediment by the end of the century.

KWONG: Holy moly, 500 million metric tons of sediment. That is a lot.

SOMMER: It's a lot. Yeah. And that's just what's normally needed, plus what's needed to deal with climate change.

KWONG: Oh, my gosh, I have a headache.

SOMMER: The natural supply will fall short of that, though - only one-third to one-half of what's needed.

KWONG: Oh, so, wait, why is it falling so short? Can we get more mud?

SOMMER: Well, there is a lot of sediment out there, but a lot is trapped before it even reaches the bay because there are these big dams, you know, built up on rivers, and their job is to store water, but they also capture the sediment in that water. So it just fills up the reservoir instead of flowing downstream. And that's a problem all over the country. You know, before you'd have these big rainstorms - right? - wash down the mud into the rivers and then it's distributed throughout all the ecosystems downstream. And human-built infrastructure has really just - it's kind of broken that cycle.

KWONG: Yeah. Like, we've disconnected ecosystems from the mud that they need to sustain themselves.

SOMMER: Yeah, yeah, it's a good way to think about it. And it's true in many watersheds, you know, basically the entire Mississippi River because, you know, you've got wetlands in Louisiana and they don't have the sediment they need from upriver. And Letitia says it's becoming a really urgent problem, actually.

GRENIER: How do we get people to see that we're on the precipice of a huge crisis? If we act now, we actually have enough sediment from other sources to keep our wetlands and to keep protecting our shorelines and to keep all these services that we've been relying on. But if we keep doing business as usual approaches, we're going to be in really big trouble.

KWONG: She makes a good point. So are there other sources of mud?

SOMMER: There are. All is not lost here. You know, some people are talking about finding ways to free up some of the sediment behind dams, you know, kind of to help it flow downstream. And there is another big source of sediment that's readily available. In fact, there's millions of cubic yards of sediment that are collected every year.

KWONG: Oh, that sounds promising. Who's doing that?

SOMMER: Well, it has to do with the hundreds of ships that come into San Francisco Bay, and they follow navigation channels. Those channels have to be dredged so they stay deep enough for the big ships. So there are these boats that go around and they either kind of scoop up or they suck up millions of cubic yards of sediment every year.

KWONG: I mean, that sounds like a perfect solution, but I feel a but coming here, Lauren.

SOMMER: Well (laughter)...

KWONG: Oh, no.

SOMMER: The problem is that most of it is dumped. It's disposed of and kind of taken to these sites and then just released underwater.

KWONG: Oh, no.

SOMMER: Yeah. It's not really useful for the ecosystem if that happens because, you know, one of those sites is actually out in the Pacific Ocean. It's not even in the bay. And there are a number of restoration projects, you know, that are being done by local and state agencies. They want that mud.

KWONG: So wait, then why is it being dumped?

SOMMER: Well, it has to do with a mandate that the Army Corps of Engineers has. So some of those agencies have asked the Federal Army Corps of Engineers to use all that material. And the corps is who manages dredging. Tessa Beach, who works at their San Francisco district, says that when they're deciding what to do with the sediment, there's a rule they have to follow called the federal standard.

TESSA BEACH: This requires that we accomplish placement of dredge material in the least costly manner that is also technically sound and meets federal environmental requirements.

SOMMER: Basically, they have to pick the cheapest option.

KWONG: I see. So dumping it in the ocean is cheaper than taking it to a wetland restoration project.

SOMMER: Most of the time, yes, because you have to ship it a little bit farther and then you have to offload it in the right place. And it's really limiting the options for local officials who are trying to make restoration happen.

AMY HUTZEL: It is frustrating that this has been decades of trying to solve this problem.

SOMMER: I spoke to Amy Hutzel, who works at the California State Coastal Conservancy. It's an agency that does restoration projects. And she says the only way they've been able to get this material is by paying the extra cost of moving it to a restoration project or by getting congressional approval for each specific project that they're doing, you know, which is pretty cumbersome. And, you know, with climate change, she's really feeling a lot of urgency to get these projects done.

HUTZEL: We're just going to be seeing erosion of our shorelines and mudflats and marshes unless we start doing things differently with sediment.

KWONG: Yeah, it sounds like when the Army Corps pursues the cheapest option, they mean the cheapest in the short term. Are they looking at the benefits of protecting shorelines in the long term? Because that needs to happen at some point and will cost money, too.

SOMMER: No, they're not. And that's the tricky thing about climate change, right? Because it requires people and institutions to plan on those longer time frames. You know, what's the preparation we can do now that saves us money and human suffering later on, even though it's more expensive in the short term? That could be changing soon, though. Last year, Congress passed a really big water bill that had a few paragraphs about this.

KWONG: Oh.

SOMMER: It directs the Army Corps of Engineers to consider the environmental benefits of using mud when they're evaluating the cost of what to do with it. It's not in effect yet. The agency has to write guidance about how to actually implement it. But there is a lot of hope that more of this material will make it to coastal restoration because these projects can take a long time, and time is running out.

KWONG: Well, I guess a few paragraphs is better than nothing. So, Lauren, thank you for taking the time to give us the dirt on dirt itself. See what I did there.

SOMMER: Wow. Emily, we almost made it through that whole episode without a pun.

KWONG: You know, leave no pun on unearthed, right?

(LAUGHTER)

SOMMER: No.

KWONG: This episode was produced by Rebecca Ramirez, edited by Gisele Grayson and fact-check by Tyler Jones and Rasha Aridi. Thanks for listening to SHORT WAVE, the daily science podcast from NPR.

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