Hundreds of North Carolina pig farmers spent the days before Hurricane Florence spraying waste from their “poop lagoons” — open-air pits filled with hog feces — over local fields, trying to make space for the up to 40 inches of rain on its way.

If the lagoons overflow, the waste could contaminate waterways. And to be clear: The hogs in Duplin County alone — two counties over from where Florence landed Friday morning — produce almost twice as much waste as New York City every day.

North Carolina is home to one of the densest concentrations of hogs in the world — around 9 million pigs are raised on 2,100 farms in the state. Duplin, with more than 2 million animals, is the top hog-producing county in the country. Large-scale farms store their animal waste in open-air pits where the solid material sinks to the bottom, revealing a nutrient-rich liquid that is then sprayed as fertilizer onto fields.

“We are expecting a lot of rain. That’s our main concern,” said Matthew Carter, who manages 9,000 head of hog spread out on three farms in Duplin County and also works as a technician for the county’s soil and water unit. “I’ve been spraying within state limits for the last several days, and I’ve gotten my lagoons down so that I have 48 inches of space, which should be plenty.”

But if Florence results in serious flooding, like Hurricane Floyd did in 1999, there’s little the farmers can do to prevent the lagoons from filling with water and overflowing.

For farmers, draining the pits ahead of a hurricane is a race against time. Hog lagoons are required to have at least 19 inches of buffer to accommodate excess rain at all times, and farmers will pump out much more than that ahead of a storm. But after a hurricane warning is issued, farmers have to stop spraying the manure onto their fields within four hours. This is so the fertilizer can be soaked up by plants before the rain causes runoff.

Because farmers have been spraying the fields throughout the year, the lagoons can handle as much as 25 inches of rain, according to Andy Curliss, chief executive of the North Carolina Pork Council.

Hog waste flows into the waste pond at a farm that has hogs owned by Smithfield Foods in Farmville, N.C (Photo: AP Photo/Gerry Broome, File)

“If we get more than 25 inches of rain, then we’ll start to be concerned,” he told Time magazine.

This isn’t the first time farmers have had to deal with hurricanes and flooding, but the size of this storm, which weather forecasters have called “unprecedented,” has many worried.

“We’ve never seen a hurricane like this before,” said Marlowe Ivey Vaughan, a Wayne County hog farmer, in an interview with NC Farm Bureau. “So we just don’t know.”

In 2016, Hurricane Matthew inundated 39 swine and 102 poultry barns and flooded 14 poop lagoons, sending that waste into nearby waterways.

But environmentalists and farmers are most concerned about a repeat of Hurricane Floyd. That storm dumped 20 inches of rain and caused widespread flooding, rupturing of manure lagoons, and the death of 28,000 hogs. Samples taken after Hurricane Floyd found dangerous levels of illness-causing bacteria in some drinking water sources for weeks after the event.

In response, the state spent millions buying out dozens of hog farms in 100-year flood zones and closed more than 100 waste lagoons. The North Carolina Department of Environment and Natural Resources did not respond to a request for comment on plans in place for Hurricane Florence.

The practice of storing waste in these lagoons and then applying it to fields has been widely criticized by environmental groups like the Waterkeeper Alliance, which point to studies indicating that they pollute local waterways.

The majority of hog farmers in North Carolina don’t actually own the pigs — they are contract workers for multibillion-dollar food corporations like Chinese-owned Smithfield. Over 82 percent of all industrial farms are contract farmers.

According to those contracts, the company decides the exact circumstances under which the pigs are kept — the only part of the pig that legally belongs to the farmer is the massive amount of waste they generate.

More than 500 residents, many from Duplin, have filed a nuisance complaint against Smithfield over the lagoons causing harm to their quality of life. The courts ordered Smithfield to pay almost $550 million in damages. Because of a North Carolina law, the amount paid to the plaintiffs is capped at $97 million. Smithfield has appealed the decision and pushed the start date of the next trial to November.

But environmental advocates also say state regulation on waste management should be stronger. Speaking to Scientific American, a spokesperson for the state’s environmental department questioned the findings of a January study on fecal bacteria in North Carolina’s waterways.

Farmers like Carter and Morris Murphy, co-owners of Triple M Family Farms, say they have learned from past hurricanes, and in addition to draining their lagoons, they are stocking up on feed and gasoline with some considering camping out on their farms. Many hogs that died during Hurricane Floyd starved to death. Duplin County is in a voluntary evacuation zone.

“For a farmer, a hurricane is a double burden,” said Murphy. “Not only are you worried about your family and property like everyone else, but you also have to worry about your animals. The family comes first, and then the livestock.”

Chad Herring, president of North Carolina Farm Families, an advocacy group for hog farmers, declined an interview because he was rushing to secure his animals. “Right now, preparing my animals for the hurricane is the most important thing.”

And the poop lagoon struggles won’t end after Florence passes. Carter said his pits should have space to hold the excess water. But after Florence is over, farmers will have to wait until the land is dry enough to start draining their lagoons again — a process that could take weeks. The worst could come after the rain, when the lagoons are at capacity with nowhere for the millions of pounds of hog shit to go.