Culvert

How Culverts Work in Stormwater Systems

Culverts act as underground bridges for water. When you build a road across a natural drainage area, you can’t just pile dirt and block the flow. Water will find a way around or through, often causing expensive damage. That’s where culverts come in.

They’re typically made from corrugated metal, concrete, or plastic pipe. The size depends on how much water needs to pass through during heavy rains. A small residential driveway might need an 18-inch culvert, while a major roadway could require a 6-foot diameter pipe or even a concrete box culvert.

Why Property Managers Should Care

Culverts are often the forgotten workhorses of your property’s drainage system. When they’re working properly, you don’t think about them. When they fail, you’ll know immediately.

A blocked or damaged culvert can flood parking lots, wash out driveways, and undermine foundations. We’ve seen property managers face five-figure repair bills because a $200 culvert cleaning turned into a major washout during the next storm.

If your property has any roads, driveways, or paths that cross natural drainage areas, you likely have culverts. They’re also common where stormwater management systems connect to municipal drainage networks.

Common Culvert Problems

Debris accumulation is the biggest issue we see. Leaves, trash, sediment, and even small trees can block culvert inlets. What starts as a minor backup becomes complete failure during heavy rain.

Cracking and corrosion affect older culverts, especially metal ones in coastal areas. Salt air accelerates deterioration. Concrete culverts can crack from ground movement or freeze-thaw cycles in the mountains.

Poor installation causes long-term problems. If the culvert isn’t properly bedded or has inadequate slope, it won’t drain completely. Standing water leads to sediment buildup and eventual blockage.

Compliance and Regulations

In South Carolina, culverts that discharge to waters of the state may require NPDES permits under the Clean Water Act. The SC Department of Health and Environmental Control (DHEC) regulates these discharges.

Georgia’s Environmental Protection Division has similar requirements for culverts in MS4 areas. If your property is in a regulated municipal separate storm sewer system, your culverts need regular inspection and maintenance documentation.

Florida’s stormwater rules are particularly strict in coastal counties. Culverts that serve as part of your stormwater management system must meet specific design standards and maintenance requirements.

North Carolina requires culverts larger than certain sizes to have riprap or other energy dissipation at outlets to prevent erosion.

When to Call a Professional

Regular inspection should happen twice yearly, ideally before and after storm season. Look for obvious blockages, standing water that doesn’t drain, or erosion around culvert ends.

Call professionals immediately if you see structural damage like cracks, separated joints, or sagging. Don’t wait if water is backing up during normal rains, this indicates partial blockage that will worsen.

For properties with multiple culverts or complex drainage systems, annual professional assessment makes sense. Our storm drainage team can evaluate your entire system, not just individual culverts.

Culvert replacement requires proper permitting, especially for larger sizes or environmentally sensitive areas. The excavation and installation process needs specialized equipment and knowledge of local regulations.