Charleston, South Carolina is booming. The metro area’s population has grown by more than 25% since 2010, making it one of the fastest-growing regions in the Southeast. That growth is happening in a place that’s simultaneously sinking and flooding more frequently — creating water quality challenges that will only intensify.
Charleston Water System (CWS) serves about 400,000 people in the tri-county area, drawing water from the Bushy Park Reservoir and the Edisto River. The utility treats and distributes roughly 80 million gallons per day. The source water is adequate in volume but faces increasing pressure from development, sea level rise, and contamination.
Saltwater Intrusion: The Slow Crisis
The Lowcountry’s geology includes several confined aquifer systems that have historically provided excellent groundwater. But decades of pumping have drawn down water levels enough in some areas to allow saltwater intrusion from the coast.
The Floridan Aquifer system, which provides groundwater to communities throughout the Southeast, is particularly affected in the Charleston area. Rising sea levels compound the problem — the freshwater-saltwater interface is migrating inland, and aquifer recharge zones are being compromised by development.
For Charleston’s municipal supply, the surface water sources provide buffer from direct saltwater intrusion. But surrounding communities that rely on groundwater wells face increasing salinity. The South Carolina Department of Health and Environmental Control monitors the situation and has restricted new well permits in some areas.
Military PFAS: Multiple Sources
The Charleston area has a dense concentration of current and former military installations — Joint Base Charleston (combining the former Charleston Air Force Base and Naval Weapons Station), the former Charleston Naval Shipyard, and the Marine Corps Recruit Depot at Parris Island (south of Charleston).
PFAS contamination from AFFF firefighting foam has been documented at multiple facilities. Groundwater monitoring around Joint Base Charleston has shown PFAS levels above EPA limits. Some off-base areas have been affected, and the Department of Defense has been conducting investigation and remediation.
The former Naval Shipyard in North Charleston is a Superfund site with multiple contaminants including heavy metals, PCBs, and petroleum compounds in soil and groundwater. PFAS adds another layer to an already complex cleanup.
For CWS customers on the surface water supply, these groundwater contamination plumes don’t directly affect drinking water. But anyone on a private well in the North Charleston, Goose Creek, or Hanahan areas should test for PFAS.
Flooding and Infrastructure
Charleston floods. The city experiences “sunny day” tidal flooding dozens of times per year — a number that’s increasing as sea levels rise. During hurricanes and heavy rain events, flooding can be catastrophic.
Flooding overwhelms the stormwater system, can infiltrate water mains through joints and cracks, and can compromise water treatment operations. CWS has experienced service disruptions during major flood events. The utility has been investing in infrastructure hardening and system redundancy, but the challenge is structural — you can’t easily engineer your way out of a city that’s 10 feet above sea level with rising waters.
Older neighborhoods with aging water and sewer mains are most vulnerable. Cross-connections between flooded sewers and water lines, while rare, are the nightmare scenario during extreme events.
Disinfection Byproducts
Charleston’s source water — particularly the Edisto River — has relatively high levels of natural organic matter (dissolved plant materials typical of Lowcountry blackwater rivers). When this organic matter reacts with chlorine during disinfection, it forms trihalomethanes (THMs) and haloacetic acids (HAAs).
CWS has historically managed DBP compliance carefully, sometimes running close to the EPA’s maximum contaminant levels. The utility uses a combination of treatment strategies including enhanced coagulation and strategic blending to manage DBP formation. Some distribution system endpoints see higher DBP levels due to longer water residence times.
What Residents Can Do
- Know your flood risk. If your area floods regularly, your water infrastructure is under stress. Consider a whole-home filtration system that can handle post-flood water quality changes.
- Filter for DBPs. An activated carbon filter effectively reduces trihalomethanes and improves taste. This is the most relevant filter choice for most CWS customers.
- Private well owners in Berkeley and Dorchester counties: Test for PFAS, bacteria, and salinity. Military contamination and saltwater intrusion are both real risks.
- Report discolored water after heavy rain or flooding events. It may indicate main breaks or infiltration.
- Check your pipes. Homes built before 1986 may have lead solder. Test if you haven’t.
If you’re concerned about your water quality, a certified water treatment professional can test your water and help you choose the right filtration system.
See also our coverage of Columbia SC water quality and Norfolk water quality.
Sources: Charleston Water System, SC DHEC, EPA SDWIS, USGS, US Navy Environmental Programs