A drilled water well is a simple concept. It consists of a hole being bored into the earth and down into a water bearing zone. This could be fractures in bedrock, or in an unconsolidated sand/gravel deposit. The upper portion of the well is lined with a steel casing which prevents the softer overburden and rock from collapsing in, and also prevents surface and subsurface contaminants from entering the well. The casing is typically seated in bedrock and the water enters the well below the casing. In some circumstances the water is drawn in through screened or slotted casing.