Although there are still nearly one million of the old fashioned "hand-dug wells", deep drilled wells are much more reliable and provide safer drinking water. Most residential wells in our area are 6 inch diameter drilled with air rotary machines. In this drilling process, which is used in hard clay or rock formations, high volumes of air is forced through the drilling pipe and out through holes at the bottom of the drill bit. The air serves to both cool the drill bit and force cuttings up and out of the hole. Water is reached from consolidated formations, either fractured or unfractured. A coated steel casing is used in the top of the borehole above the water producing zone. The casing is sealed into the bedrock to prevent borehole collapse or to exclude water of undersirable quality. The area between the borehole and casing, or annular space, is sealed with a grout mix to prevent surface water infiltration. The well casing should extend 18 inches above grade. The well is then capped with a secure, sealed well cap.