Aquifer

An underground geological formation or group of formations containing usable amounts of groundwater that can supply wells and springs. Aquifers are more protected from contaminants than surface waters, but may still be tainted by fecal coliform from improperly functioning OWTS. Half of all Americans get drinking water from aquifers. Of these, roughly a third have their own wells, while the remainder use municipal water systems that draw on underground sources. <