How to Grade a Dirt Road. Dirt roads--by their very nature--are susceptible to potholes, ruts, corrosion and poor drainage. Grading the road's surface is one way to rejuvenate its weakening surface. Here are some steps to take if you need to grade a dirt road.
Determine the best means to control water flow by watching your dirt road closely during a rainstorm. Knowing the natural path the water takes will make grading more effective.
Crown your dirt road by making the center of its road bed higher than its sides. This allows water to drain from the center to the sides of the road.
Harness and guide water away from the road by digging a roadside ditch if the land's contour warrants it. Slope the ditch's bank from the road's edge to the bottom of the ditch at an angle that is at least three inches in a foot so the water doesn't flow back on the road.
Make the ditch's width and depth a minimum of one foot. If your dirt road is located in a heavy runoff area you'll need a larger ditch.
Create a "grade dip" to direct the water--that's in the ditch or washing down the hillside--across the road. This is done by digging a shallow ditch traversing the road and lining it with rock. Mound the excess dirt across the road's downgrade side to form a bump to prevent the water from running down the road. Instead, the water will travel off the dirt road through the "grade dip."
Construct the "grade dip" a minimum of 70 feet wide; that includes the width of the ditch and mound. Make the ditch roughly 50 feet wide and the mound a minimum of 20 feet with a 30 degree rise. In cases where the dirt road's uphill grade is steeper than five percent, increase the width of the "grade dip" five feet for every one percent of grade rise.