Horry County Septic Challenges: Growth & Flooding

Horry county septic systems face a convergence of challenges that make this South Carolina's most complex county for onsite wastewater management. As the state's fastest-growing county — home to Myrtle Beach, Carolina Forest, Conway, and dozens of rapidly expanding communities — Horry County is adding thousands of new homes annually, many in areas that depend on septic systems. Simultaneously, the county's low-lying Coastal Plain geography, high water tables, and devastating flood history create conditions that stress even well-designed septic systems to their limits.

From the Waccamaw River's repeat flooding to the ongoing expansion of sewer infrastructure in the Myrtle Beach corridor, understanding horry county septic challenges is critical for current homeowners, prospective buyers, and builders planning development in this booming coastal market. This guide covers the specific factors that make septic systems in Horry County uniquely challenging and what homeowners can do to protect their properties.

Horry County Septic Problems: The Growth-Infrastructure Gap

Horry County's population has grown by more than 40% since 2010, making it South Carolina's fastest-growing county by percentage. Communities like Carolina Forest, Forestbrook, Socastee, and the Conway area have seen explosive residential development. Much of this growth has occurred in unincorporated areas outside Myrtle Beach's municipal sewer service territory, meaning thousands of new homes rely on individual septic systems.

The pace of development has created horry county septic problems that stem from the sheer volume of new systems being installed in marginal soil conditions. The county's Coastal Plain soils — predominantly sandy with high water tables — can support septic systems when properly designed and installed. But when development density increases, the cumulative impact of thousands of systems discharging treated effluent into the shallow groundwater can degrade water quality in nearby waterways, particularly during wet periods.

Grand Strand Water and Sewer Authority (GSWSA), the region's largest utility, has been expanding sewer service into previously septic-dependent areas, but infrastructure expansion cannot keep pace with development. Many neighborhoods built in the 2000s and 2010s with individual septic systems are now candidates for sewer extension, but the cost of retrofitting established neighborhoods with sewer lines is substantial — often $10,000 to $20,000 per lot for the utility's infrastructure, plus individual connection costs for homeowners.

Horry County Flood Septic Damage: A Recurring Crisis

Flooding is Horry County's most significant threat to septic system integrity. The county has experienced catastrophic flooding events repeatedly in recent years — Hurricane Matthew (2016), Hurricane Florence (2018), and subsequent storms and inland flooding events that devastated communities along the Waccamaw River, Kingston Lake, and their tributaries.

When horry county flood septic damage occurs, the consequences are severe and long-lasting:

Floodwater infiltrates septic tanks through access ports, inlet and outlet pipes, and any compromised joints or cracks. This fills the tank with contaminated floodwater, dilutes the biological treatment process, and can flush untreated sewage out of the tank and into the saturated drain field or directly onto the ground surface.

Drain fields become completely saturated — not just with effluent from the home's septic tank but with regional floodwater. A drain field cannot treat effluent when the surrounding soil is already saturated. During and after flooding, the drain field effectively stops functioning, and any wastewater entering the system has nowhere to go.

Empty tanks can float during flooding. When the ground is saturated and the water table rises above the bottom of the tank, hydrostatic pressure can lift an empty or partially empty concrete or fiberglass tank out of the ground, severing all pipe connections and causing catastrophic damage. This is why homeowners should never pump their tank during or immediately after flooding.

Conway, located at the confluence of the Waccamaw River and Kingston Lake, has been particularly hard hit. Neighborhoods in the conway sc septic service area along the Waccamaw floodplain have experienced repeat flooding that damaged or destroyed hundreds of septic systems. Some homeowners have rebuilt or replaced their systems multiple times, prompting calls for expanded sewer service in flood-prone areas.

High Water Tables in Horry County

Even without flooding, Horry County's naturally high water table creates ongoing challenges for septic systems. In many parts of the county, the seasonal high water table is within 12 to 24 inches of the ground surface — far shallower than the 36 to 48 inches that provides ideal conditions for conventional septic system operation.

A high water table reduces the vertical separation between the drain field and the groundwater, limiting the soil's ability to filter and treat effluent before it reaches the water table. SCDES requires a minimum of 24 inches of separation between the bottom of drain field trenches and the seasonal high water table. In many Horry County locations, this requirement can only be met by raising the drain field above natural grade using mound systems or by using advanced treatment units that produce cleaner effluent requiring less soil treatment.

The water table in Horry County fluctuates seasonally and is heavily influenced by rainfall. During wet periods (typically late summer through early fall — also hurricane season), the water table can rise to within inches of the surface in low-lying areas, essentially turning a functional drain field into a saturated mess. This seasonal fluctuation means that a system installed during dry conditions may struggle during wet periods when the water table is highest.

Well Water Quality in Coastal Horry County

Private wells in Horry County tap shallow coastal aquifers that present unique quality challenges. The proximity to the Atlantic Ocean creates saltwater intrusion risk, particularly for wells near the coast or on barrier islands. Wells that are drilled too deep or pumped too aggressively can pull brackish or salty water into the wellbore, rendering the water unusable.

Typical well depths in Horry County range from 30 to 150 feet, drawing from unconsolidated sand and shell aquifers. Water quality concerns include elevated chlorides (from saltwater influence), iron and manganese staining, hydrogen sulfide (sulfur odor), and bacterial contamination from the shallow water table's vulnerability to surface contamination. The high density of septic systems in developed areas raises additional concerns about nitrate contamination of shallow groundwater that feeds nearby wells.

Homeowners with wells near areas with high septic system density should test for nitrates annually in addition to standard bacteria testing. For comprehensive guidance, browse our Horry County septic and well water directory and our detailed article on Myrtle Beach and Horry County septic services.

SCDES Enforcement in Horry County

Horry County's combination of rapid growth, flood damage, and environmental sensitivity has made it a focus area for SCDES enforcement. The agency's Coastal Regional Office handles a high volume of permit applications, complaint investigations, and post-disaster assessments in Horry County. Common enforcement actions include citations for unpermitted septic system installations or repairs, systems that do not meet the permitted design specifications, and failing systems that are discharging untreated effluent onto the ground surface or into waterways.

After major flooding events, SCDES conducts systematic assessments of septic systems in affected areas, identifying damaged systems and requiring repairs or replacements. In some cases, SCDES has worked with FEMA to facilitate funding for septic system repairs and replacements after federally declared disasters. Homeowners with flood-damaged systems should document all damage with photographs and contact SCDES for guidance on repair or replacement permit requirements.

For additional resources on Horry County's coastal septic challenges, see our in-depth article on the coastal South Carolina septic crisis.

Sewer Expansion and the Future

Grand Strand Water and Sewer Authority and the City of Myrtle Beach have been actively expanding sewer service into areas previously served by septic systems. Priority areas include flood-prone neighborhoods along the Waccamaw River, high-density development corridors, and environmentally sensitive areas near tidal creeks and the Intracoastal Waterway.

Sewer expansion benefits the entire community by reducing the groundwater contamination risk associated with thousands of individual septic systems and eliminating the flood-damage cycle that destroys septic systems and creates public health hazards. However, sewer connection costs for individual homeowners can be substantial — typically $3,000 to $10,000 for the connection fee plus $3,000 to $7,000 for lateral installation from the house to the new sewer main.

For homeowners in areas where sewer expansion is planned but not yet available, investing in a high-quality septic system with enhanced flood resilience makes sense. This might include elevated system components, watertight risers and access ports, and an advanced treatment unit that produces cleaner effluent requiring less drain field area. While more expensive upfront, these features can prevent costly flood damage and position the property for easier sewer conversion when service becomes available.

Frequently Asked Questions

How does flooding affect my septic system in Horry County?

Flooding overwhelms septic systems in multiple ways: floodwater infiltrates the tank and dilutes the biological treatment process, the drain field becomes saturated and cannot absorb effluent, and the system may discharge untreated sewage onto the ground surface or into floodwaters. In severe cases, hydrostatic pressure from saturated soil can float empty tanks out of the ground. After flooding, do not pump the tank until the ground has dried (1 to 2 weeks post-flood), then have the system professionally inspected for damage.

Is Horry County expanding sewer service to replace septic systems?

Yes. Grand Strand Water and Sewer Authority and the City of Myrtle Beach are actively extending sewer service into previously septic-dependent areas, with priority given to flood-prone neighborhoods, high-density developments, and environmentally sensitive zones. However, expansion is a multi-year, multi-million-dollar process, and many areas will continue to rely on septic systems for years to come. Homeowners in planned expansion areas may want to coordinate with the utility before investing in major septic system repairs or replacements.

What type of septic system works best in Horry County's high water table?

Mound systems and advanced treatment units (ATUs) are the most common solutions for Horry County's high water table conditions. Mound systems raise the drain field above natural grade, providing the required separation between the drain field and the water table. ATUs produce higher-quality effluent that requires less soil treatment, allowing installation in tighter conditions. Both options cost significantly more than conventional systems — $10,000 to $25,000 compared to $4,000 to $8,000 for a conventional system — but they are often the only viable option in low-lying Horry County properties.

How much does septic pumping cost in Horry County?

Septic pumping in Horry County costs $275 to $400 for a standard 1,000-gallon tank during regular business hours. After-hours or emergency pumping costs $400 to $600 or more. The competitive market in the Myrtle Beach area helps keep pricing in line with state averages. Pumping is recommended every 3 to 5 years for typical household use, though homes in flood-prone areas may need pumping more frequently after flood events. SCDES recommends keeping pumping records as part of your system maintenance documentation.