Grease, oils and disposable wipes are taking a toll on Charleston-area sewer systems

NORTH CHARLESTON — When Lowcountry cooks flush their leftover cooking grease down the drain, they may not be thinking of what lies beneath.

But at some point during its journey into the sewer system, the fat cools, solidifies and mixes with flushable wipes. The result is a giant, stinking mess.

Fats, oils, grease and flushable wipes can be damaging to sewer systems. But utilities like the North Charleston Sewer District try to nip potential problems in the bud. This week, the utility began sucking huge globs of wet grease, fats and wipes from the Popperdam Pump Station off Dorchester Road.

The ultimate responsibility lies with anyone who flushes a toilet or uses a sink. Human waste and toilet paper are the only things that should be flushed into a home plumbing system, said Baker Mordecai, who oversees wastewater collection of Charleston Water System.

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The solidified fats and other items cause the problems.

Fried bacon, for example, often leaves behind a layer of grease in cookware. When the grease is no longer hot, it becomes a white, thick, oily substance.

Some people will pour the hot grease into a can or jar and use it the next time they cook green beans or collards. It solidifies no matter where it cools. When mixed underground with wipes and other items, the grease can clog pipes.

Discarded cooking fats should cool in a sealed bottle or can and be disposed of at a recycling center or in household trash, according to Clemson Cooperative Extension. Any remnants of grease and oil left in dishes can be removed by scraping and absorbing them with a paper towel.

Hot water and soap will not eliminate grease. The substance will only reform and solidify in pieces.

"As that (discarded fat) makes its way into the system, it collects with other grease and it collects with what we call flushable wipes — which, just because something says you can flush it doesn't mean it should be flushed — and they together create like a large solid mass," said Katie Callahan, director of Clemson University's Center for Watershed Excellence.


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This large mass can be a thick, oily, stringy blob underground. And in some instances, it looks like a big pile of wet mud with pieces of white paper products mixed within. The smell resembles the cow manure used to fertilize crops.

That large mass, sometimes called a "fatberg," can attract rodents into the systems and create a public health hazard. If sewage backs up behind the large mass, manholes may overflow and pour untreated wastewater into rivers and estuaries.

Grease, oils and disposable wipes are taking a toll on Charleston-area sewer systems

Inside your house, the problem could result in the need for and expense of a plumber.

Environmental stewards like Callahan want to minimize any chance of raw wastewater entering the state's waterways because the sewage contains pathogens and viruses.

"So if you swim in waterbodies that are polluted with raw wastewater, you can get swimmers ear, you can get gastrointestinal illnesses, rashes, eye irritation, and it's dangerous for pets, like our dogs, who swim as well," Callahan said.

On March 8, reporters watched as workers with the North Charleston Sewer District used long shovel-like tools to break up masses in the wet well. Dressed in white hazmat suits, the men took turns navigating an excavator to scoop out the top layer or gunk and dump it onto the surface. The rest was vacuumed out.

The Sewer District works continuously to prevent fats, oils, grease and wipes from becoming a big solid mess underground.

Masses are removed from the district's large pump stations about every year and a half. Smaller stations need more regular attention.

"It can get so bad, so thick and so hard that if you were to walk on it, you could," said Caitlin Graham, who's responsible for managing the clogs for the North Charleston Sewer District.


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To start the removal process, crews take an excavator to dig up as much of the top layer of mass as possible. The rest is sucked up with a Vactor truck and taken to a wastewater treatment plant.

The utility spends $100,000 to $200,000 a year to manage solidified fat and wipes at stations like Popperdam, which is off Dorchester Road. The wet well there can hold about 250,000 gallons. Only one other pump station in the district can hold that much. There are 55 other stations that are much smaller and less costly to maintain.

Sewer workers hope to remove about 30,000 gallons of fat and wipes from the Popperdam sewage well over the next few weeks, Graham said.

Charleston Water System, which provides sewer service to the city of Charleston, has focused on preventive maintenance. Over time, CWS has increased how often it cleans wet wells and sewer lines, and has installed bar screens to remove wipes to protect the treatment plant.

Mordecai said CWS has seen a 44 percent increase in its cleaning costs since the start of the pandemic. It now spends about $360,000 annually, Mordecai said.

Although the water system does not advise against using disposable wipes, it does urge people to avoid flushing them down the toilet. Mordecai said some wipes are mislabeled, claiming to be flushable even though they aren't.

CWS removes about 600 wheelbarrows of wipes and solid fat per year.

"It actually collects in our wet wells, in our manholes, in our bar screens and other places where it has to physically removed," Mordecai said. "And it's a very expensive proposition to do that."

The cost is so cumbersome that the water system was a lead plaintiff in a lawsuit filed in 2021 against the Kimberly-Clark Corp., a leading manufacturer of flushable wipes, and other companies that market and sell these products. CWS alleged the "flushability-related claims" made on the labeling and packaging of the wipes were false, deceptive or misleading.

CWS and Kimberly-Clark have since agreed that Cottonelle flushable wipes, produced by the corporation, will adhere to a municipal wastewater industry standard for what can be flushed by May 2022.

Although Cottonelle wipes are OK to be flushed, most other wipes aren't, and fats, oils and grease likely never will be.