Typically, groundwater is naturally clean and safe for use because of the top layer of soil that acts as a natural filter. However, contamination may occur improper installation of well casings or caps, after a break in the casing, or as a result of contaminated surface water entering the well. Contamination can also occur if water wells are drilled in fractured bedrock without enough protective soil and with less than the recommended minimum casing length. Additionally, contamination can occur over time as more and more wells are drilled into the same aquifer (water-bearing layer). Water wells should be properly maintained and the water tested regularly to ensure the safety and quality of your water supply and to prevent the possibility of illness.