Impervious Surface
Impervious surfaces are areas that don't allow water to soak into the ground. Think pavement, rooftops, concrete walkways, and pool decks. When it rains, water runs off these surfaces instead of absorbing naturally into the soil, creating stormwater runoff that needs to be managed.
How Impervious Surfaces Work
When rain hits natural ground like grass or dirt, most of it soaks in. But when it hits your parking lot, building roof, or sidewalk, that water has nowhere to go except sideways. It picks up speed, collects pollutants, and flows toward storm drains, retention ponds, or nearby waterways.
The more impervious surface you’ve on your property, the more stormwater runoff you’re creating. A small shopping center might generate thousands of gallons of runoff from a single inch of rain.
Why Property Managers Should Care
Impervious surface coverage directly impacts your stormwater management requirements. Most coastal communities calculate stormwater fees based on how much impervious surface you’ve. More coverage means higher fees and stricter compliance requirements.
In Charleston County, properties over certain impervious surface thresholds must install and maintain stormwater control measures. Beaufort County has similar requirements. Your property’s impervious surface percentage determines whether you need retention ponds, bioswales, or other stormwater management systems.
Common Issues to Watch For
Cracked or deteriorating pavement can actually become semi-pervious, but not in a good way. Water seeping through damaged asphalt can cause erosion underneath, leading to sinkholes or structural problems.
Conversely, well-maintained impervious surfaces that drain properly protect your property’s foundation and prevent flooding. The key is directing that runoff to appropriate collection and treatment areas.
Watch for standing water on impervious surfaces after storms. This usually indicates drainage problems that need attention. Poor drainage can lead to property damage and regulatory compliance issues.
Compliance Requirements
South Carolina’s Stormwater Management and Sediment Reduction Act requires most developments to manage runoff from impervious surfaces. The NPDES Municipal Separate Storm Sewer System permits in cities like Hilton Head and Savannah include specific requirements based on impervious surface coverage.
Georgia’s Environmental Protection Division has similar rules. In Florida, properties with significant impervious surfaces often fall under stormwater utility ordinances that require regular BMP inspections and maintenance.
Failing to properly manage runoff from impervious surfaces can result in violations, fines, and expensive remediation requirements.
When to Call a Professional
If you’re seeing erosion, standing water, or drainage issues around your impervious surfaces, don’t wait. These problems typically get worse with each storm event.
A qualified stormwater contractor can assess your property’s impervious surface coverage, evaluate your current drainage systems, and recommend solutions that keep you compliant while protecting your investment. Professional storm drainage design considers not just current requirements but future expansion and changing regulations.
Related Terms
Best Management Practice
A Best Management Practice (BMP) is a proven method or structure designed to control stormwater runoff, prevent pollution, and protect water quality. BMPs include retention ponds, swales, filters, and other systems that capture and treat rainwater before it reaches streams, rivers, or groundwater.
Drainage Easement
A drainage easement is a legal agreement that gives someone the right to use part of your property for water management purposes. This could include installing pipes, channels, or retention areas to handle stormwater runoff from neighboring properties or public areas.
Related Services
Frequently Asked Questions
How do I calculate the impervious surface coverage on my property? expand_more
Can I reduce my stormwater fees by decreasing impervious surface coverage? expand_more
What happens if my impervious surfaces are causing drainage problems? expand_more
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