Radial increment of dominant and codominant oaks increased 17 percent over that expected on a ridgetop of the Appalachian Plateau after a four-year period of campground sewage effluent spray irrigation. Data were collected from randomly selected dominant and codominant northern red oak, chestnut oak, and white oak trees. Increment cores from each tree were used to determine the annual ring width for the four-year period, and the preceding six years.