How to Dig a Trench Into a Gravel Driveway
Gravel driveways offer a permeable surface that helps prevent water from accumulating on the surface, but drainage problems can still develop. Once water seeps through the foundation, the ground below becomes saturated and the gravel will begin to wash away. Digging a trench through the driveway enables you to lay underground drain pipes that will distribute the water to other areas of the yard.
Examine the gravel driveway after a rainfall, and mark off the area where water stands for more than an hour with a garden stakes. Draw an L-shaped course for the drainage system by laying a long rope on the ground from the problem area to the low-lying side of the driveway and down to the street.
Dig out a trench 10 inches wide through the driveway with a shovel. Dump the removed gravel on a nearby tarp to fill in the trench with once you’re done. Dig out 18 inches of gravel from the trench. Slope the bottom toward the low-lying side by digging a smooth slope on a 1/8-inch decline per every horizontal foot.
Dig out another 10-inch wide trench along the side of the driveway to connect with the first trench. Scoop out the grass and dirt with a shovel and keep it on another tarp. This trench should be 18 inches deep and sloped toward the street.
Tamp the bottom of both trenches with the flat end of a 4-by-4-inch board. Lay synthetic filtration fabric over the bottom of each trench to keep silt from floating up into the drain pipes.
Shovel 6 inches of gravel into both trenches and tamp it down. You’ll need to purchase new gravel to fill the trench along the side of the driveway.
Arrange 4-inch PVC perforated pipes down the center of the trench. Connect lengths of pipe with tee, wye or elbow fittings depending on the angle of the joint.
Cover the pipes with another 6-inch-thick layer of gravel, and layer filtration fabric over the top to block silt and debris from seeping down.
Fill in the remaining trench running across the driveway with gravel, and tamp it down so it's level with the rest of the driveway.
Pour soil into the remaining hole along the side of the driveway, and plant the grass back over the soil so it doesn’t erode.