When rain comes down in some parts of Charleston, S.C., sewage comes up. In the neighborhood of West Ashley, storms trigger waste overflows so often into a pond near Nell Postell’s home that she has a wet-weather routine based on forecasts: she buys surgical masks, clears her garden and then listens for the sewage to “gush”: her signal to phone local authorities.

“All I’ve got to do is tell them the sewer is in the pond. I don’t even have to give them my address,” said Postell, a longtime resident. “They know my address.” Overflows run down a gully next to Postell’s house, over her yard and into the pond, leaving visible human feces, noted in pollution reports as “floatables.” 

“It smells like you’re living in a portaloo,” Postell said.

When the rain stops, she said, a team from Charleston Water Systems arrives with disinfectant. Sometimes the workers swill it from buckets over her yard and the pond. When the overflow is particularly voluminous, they spray chemicals from a tanker truck into the water and onto its banks near wax myrtles and oak trees. “I wonder if it’s a health problem,” Postell, an avid gardener, said. “I don’t know whether my ground is contaminated.”

Last month the nonprofit watchdog Charleston Waterkeeper accused the public utility of breaking federal environmental law by allowing tens of thousands of gallons of raw sewage to leak, spill and overflow across the city every year. Each overflow represents risks to residents and local rivers—and violates the Clean Water Act, it said in a Feb. 28 letter of intent to sue the water company, the first step in a possible legal challenge. 

Charleston Water has reported 176 sewage spills of more than 500 gallons since 2015. The manhole that overflows near Postell’s house is one of its weakest links, with 11 overflows in the past three years, according to Charleston Water’s reports to the state Department of Health and Environmental Control (DHEC).

“These are basic infrastructure things: how you handle sewage waste,” Waterkeeper’s director Andrew Wunderley said. “Not only is it a water quality issue, it’s a plain old public health issue. That’s untreated sewage and all the bacteria and pathogens that come with it.”

Charleston’s predicament illustrates a dynamic climate risk: South Carolina, along with much of the eastern United States, is experiencing more frequent bouts of more intense rainfall as well as an accelerating sea level rise. The overflows have been reported for decades, but Wunderley and lawyers at the Southern Environmental Law Center, which is representing Charleston Waterkeeper, now fear that climate change will push aging infrastructure to a breaking point. 

The nonprofit’s letter of intent to sue demands the utility present a plan to prevent sewage spills within 60 days, a response time set by federal regulation. If the water company fails to meet that planning deadline, at the end of April, the nonprofit can file suit in federal court.

“There are clear violations of federal law ongoing right now,” Catherine Wannamaker, an attorney with the Southern Environmental Law Center, said. “Charleston Water has been working on it but it’s taking too long and these problems really need to be fixed.”

“Climate change is really exposing the inadequacies of our existing systems to handle the new normal,” Wunderley said.

Charleston’s wastewater system is designed to keep sewage and storm water separate. But Charleston Water acknowledges that “cracked pipes, damaged manholes, [and] improper storm drainage connections” all create leaks in the system. During storms or floods, excess water overpowers the system and hundreds of gallons of sewage flow freely into the streets, sometimes with enough power to blow manhole covers. 

“Charleston Water is unable to accommodate rain events, tidal surge, and floodwater in a city plagued by frequent and intense storms and flooding,” the letter of intent says “This issue will only grow worse as the impacts of climate change fuel worse storms and as the sewer system continues to structurally deteriorate.”

The letter alleges that Charleston Water is undercounting spills—and it specifically references an overflow in December 2023 that residents filmed but the utility did not report to state regulators. The letter also expressed suspicion about some of the utility’s reporting, noting that recorded overflows caused by blocked pipes have decreased in the past decade for no apparent reason.

“Unless a highly effective cleaning program—which has not happened to Charleston Waterkeeper’s knowledge—the number of blockage SSOs are almost certainly higher than Charleston Water is reporting to DHEC,” according to the letter, referring to sanitary sewer overflows.

“Climate change is really exposing the inadequacies of our existing systems to handle the new normal.”

Mike Saia, a spokesperson for Charleston Water, acknowledged the letter and responded in an email to Inside Climate News that “overflows are never an acceptable outcome,” and that the utility has an ongoing, multi-hundred million dollar project to increase the system’s capacity.

Residents said Saia’s assurances are underwhelming. “I have been living with this and it’s been a problem for a long, long time,” Postell said. “They said it’s going to take four or five years for them to correct the problem, and now they’re saying two or three or four more years. God knows when they are ever going to be able to fix it.”

Wannamaker, the Southern Environmental Law Center attorney, said residents are tired of waiting. “I know that they’re aware of the problem and they have been working on it but from our perspective it’s taking too long,” she said. “They’ll say ‘we’re working on it’ and I don’t doubt that, but it can’t just be 10 years of ‘we’re working on it.’”

The utility has in the past appeared to blame increased development, restaurant grease and unflushable wipes for the spills. Lawyers, advocates and scientists are clear that Charleston’s sewers are being broken by climate change in two specific ways.

Located in South Carolina’s Lowcountry, Charleston is one of the state’s frontlines for accelerating sea level rise. “It’s a city that’s plagued by geography,” Wannamaker said, “but the tidal influence has definitely gotten more serious.”

During floods or some heavy rain, water can seep into the ground around the sewage pipes, and penetrate corroding pipes and pumping equipment. The more salt-laden seawater there is in the ground, the more corrosion is likely.

Scientists predict Charleston will experience a dramatic sea-level rise in the next three decades—more than the past century altogether. Historic tide gauge data from Charleston Harbor documents a one-foot rise in the past hundred years. Before 2050, the city will likely face another 14 inches, according to projections calculated in 2022 by the National Oceanic Atmospheric Administration.

While less salty, rainwater can also seep into sewage pipes and cause overflows. Along with much of the eastern United States, South Carolina is experiencing more frequent bouts of more intense rainfall.

“It’s a simple physics relationship,” explained J. Marshall Shepherd, director of the University of Georgia’s atmospheric sciences department. “As the atmosphere warms it has greater water vapor capacity. So as our climate system warms, these storms have more water vapor available to them. That’s an ingredient for more intense rain.”

Charleston is not unique, Shepherd said. “This lines up with what we’re seeing all throughout the South when it comes to sewage and septic systems.”

In the southeast specifically, heavy storms—those that produce more than an inch of rain—have become 50 percent more likely since the start of the century, according to scientists at a benchmark federal climate conference last year.

In August 2022 the Pearl River in Jackson, Miss., broke its banks after consecutive days of downpours that disabled the city’s largest water treatment plant, which left 150,000 city residents without water. Residents were boiling water for more than a month, and critics said the problems in Jackson, where 80 percent of the population is Black or brown, revealed racial inequities in infrastructure quality and safety. 

In Charleston, overflows are now occurring with some regularity, the letter of intent said, adding “more concerningly, a majority of the wet-weather SSOs occurred during relatively routine rain events.” 

 Analysis by the Southern Environmental Law Center shows that more than 40 percent of the wet-weather overflows were triggered by “one-year storms,” a weather event defined by meteorologists as statistically certain to happen in Charleston at least once a year.

Charleston Water’s spokesperson Saia noted that the utility has recorded increased pressure from sea level rise, but he said there are questions about what and who to blame. “We don’t have definitive data about climate change and how it impacts our operations, or more specifically inflow and infiltration, as that’s extremely difficult to quantify,’ he said in an email to Inside Climate News. 

“We see tidal influence on inflow twice a day, and that gets higher as seas rise due to increased groundwater pressure, but there’s so many other contributing factors that are difficult to separate out.” Other sewage systems in the region are buckling under infrastructure failures alone. 

In Tuscaloosa, Ala., 42 million gallons of sewage have spilled onto the streets since 2018. Most overflows occurred in calm weather, suggesting a general lack of maintenance, particularly in low-income, Black communities. The Congaree River in South Carolina was doused with more than four million gallons of sewage in 2023, much of it released during a power failure at a wastewater treatment plant. The influx equaled 10 times the waste recorded in 2022.

Charleston Water has said some backups occur because of insoluble junk flushed into its pipes by customers. For the past three years, the utility has spent $1.2 million just removing sanitary wipes that jam its pipes. The utility alleged in court in 2021 that seven companies—from Costco and Target to CVS—sell “flushable” wipes which “are not actually flushable.” Charleston Water did not seek fines against the companies and the companies agreed in a recent court settlement to change their labeling on some products. 

Wannamaker said fretting over wipes is a distraction from a more dire problem. The city needs to address rising waters as the biggest stress on its system and the safety of its residents, she said.

“If wipes were the whole problem, every sewer system in the United States would have that problem,” Wannamaker said. “Of course you need resources to fix all of this, but they have not adequately prioritized.”

Wannamaker and Wunderley both said land development is also straining the sewage system. According to Census Bureau data, South Carolina is the fastest growing state in the nation, with much of its growth concentrated in coastal counties like Horry or Charleston.

Environmental advocates note there is lax regulation of septic tanks in rural and coastal areas. Rising seas and heavy rains are adding to the risks to lakes and rivers there, they said.

Developers can build up to three septic tanks on an acre of land, and only six inches of “separation distance” is required. Separation distance is the space between a septic system and the natural level for underground water. When rain falls and the level rises, critics say six inches is not enough of a barrier between sewage and groundwater. 

Wunderley said South Carolina allows “some of the weakest septic tank regulations in the southeast.” Developers have been able to build coastal housing with a high density of septic tanks, which are vulnerable during heavy rain and flooding, he said. In neighboring North Carolina, developers are limited to one tank per acre and the separation distance must be at least a foot.

Just north of Charleston, a development under construction in the fishing town of Awendaw has been approved to build homes with more than 400 new septic tanks on less than 200 acres, all next to a wildlife refuge. 

Wunderley, who often tours the Charleston River, said he sees the effects of septic pollution in the water. There are harmful algae blooms and shellfish beds have been tainted and closed.

As part of a separate lawsuit in 2022, Charleston Waterkeeper and the conservation league alleged that the DHEC unlawfully permitted septic tanks in coastal zones that are particularly vulnerable to flooding.

DHEC declined comment on the case, and the state Administrative Law Court has not yet reached a judgment. Since the suit was filed, 44 septic tanks have been permitted at Awendaw.

In Charleston, utility spokesperson Saia said he hopes the sewage overflow disputes will not spill into court. “We look forward to and hope for collaboration instead of litigation,” Saia said in an email, “as that brings the most benefit to the environment.”

“We are not a group that sends notices of intent to sue just for the heck of it,” Wannamaker said. “We are starting to have some initial conversations with Charleston Water System about how to resolve this. One of the things we’re looking for here is a clear path with a concrete timeline to fixing these problems.”