A culvert is a pipe placed in the ground to carry water under a road or driveway. If a roadway has a drainage ditch alongside it, a culvert will be needed for each driveway that crosses the ditch. Larger culvert pipes may go underneath the road itself or may be used to divert water around parking lots. Because of their proximity to moving water the areas around culverts are prone to erosion, especially if the culvert pipe is not installed correctly or is too small. Make sure the pipe is kept free of obstructions and be aware of ways to minimize erosion.
When Installing a Culvert
Choose a culvert pipe that has a large enough diameter to accommodate the water.
Cut the pipe longer than the driveway or road it will span, so the ends stick out beyond the bank.
Excavate deep enough, so the bottom of the pipe is level with the bottom of the drainage ditch. Position the pipe, so the upstream end is higher than the downstream end.
Backfill, so there is at least 12 inches of dirt and fill above the pipe or dirt that is as deep as half the pipe's diameter, whichever is the larger measurement. Pack the dirt firmly around the pipe.
Steps Taken with Existing Culverts
Place a layer of large rocks against the earth around both ends of the culvert pipe to keep the soil from being exposed.
Plant vegetation along the bank. The roots of the vegetation will help keep the soil in place. This step and the one above are relatively inexpensive steps. If you have persistent erosion problems, take the more expensive step below.
Place a layer of geotextile material on top of the soil along the bank in the area prone to erosion. Place rip-rap on top of the geotextile material. Rip-rap is a man-made product consisting of biodegradable bags of cement base that mold to the shape of the ground underneath them and will eventually become solid. Place rip-rap in layers, interlocked like bricks to form a sturdy retaining wall.