Can South Carolina's sewage systems adapt to a changing climate?

As it meandered across South Carolina’s Lowcountry in August 2024, Tropical Storm Debby left a wake of sewage in its path. The storm’s heavy rainfall spurred dozens of sanitary sewer overflows across the state.

In a warming world, South Carolina could experience many more storms like Debby — drenching rain events that provoke troublesome and dangerous sewage spills.

These overflows occur when stormwater infiltrates a sanitary sewage line, causing the system to become over-burdened and blow back untreated or partially treated sewage. That sewage then washes into the state’s rivers, streams or lakes where it can create hazardous swimming and fishing conditions.

These kinds of overflows are common. The S.C. Department of Environmental Services estimates that the state experiences about 600 such events annually. They often coincide with bouts of heavy rain.

As the climate warms, tropical storms are forecast to become stronger, and some are likely to move slower. And extra-intense rainstorms, or “rain bombs” as they are sometimes called, are becoming more frequent in most of the U.S. because warmer air collects more moisture that eventually is released with more force.

“ When we have more severe storms, that means a higher volume of storm water in a short amount of time, overwhelming our sewer systems … particularly when we’ve paved over everything,” said John Rumpler, the clean water director at the advocacy group Environment America.

Baker Mordecai, chief operating officer of Charleston Water System, said the utility can go weeks or months at a time without experiencing an overflow. But all it takes is one bad day.

Mordecai said the threats climate change poses aren’t just a concern of the water system.