Groundwater is a hidden source of water, stored in underground geologic formations, through which water passes slowly. Two primary types of geologic formations, or aquifers, from which groundwater can be pumped are sediments and fractured rock. Sediments are composed of layers of sand, rock, and clay, are found in valley and coastal areas and can store vast quantities of water. Fractured rock aquifers yield smaller amounts of water and occur near mountain ranges that were fractured by volcanic eruptions or movements of the earth's crust.

    Water (from precipitation or irrigation) which can not be absorbed by the soil or used by vegetation eventually finds its way into the groundwater basin. The water percolates through the sediment until it reaches material which it can not penetrate. This is where water accumulates, creating an aquifer, or what we call a saturated zone. The water table is located at the top of the saturated zone.

    A well is a hole drilled into an aquifer, like the one described above, by a water supplier. Typical wells range from 50 feet deep to 2,000 feet deep and can be a sole source of drinking water for a community or used to supplement the existing surface water supply. Simply put, a pump pulls water from the well into a pipe that brings water to the surface. A screen keeps rocks from getting into the pipe.

    The City of Redding Water Utility utilizes vertical turbine or submersible turbine pumps, both designed to pump water from deeper wells. Our wells range from a depth of 170 feet to a depth of 600 feet below the surface. There are currently 19 wells in operation, located in the southeast and southwest areas of the City. These two areas are known as the Enterprise Zone and the Cascade Zone, respectively.

    Nature's process of filtering water through layers of rock and sediment, in general, produces high quality drinking water that needs only to be disinfected before use. There are times, however, when pollutants overwhelm nature's ability to filter out contaminants. This is of great concern to many communities who rely solely on groundwater.

    Wells can become contaminated in a number of ways. If the well is not properly constructed or maintained, pollutants can contaminate the aquifer the well was drilled to tap. Fuels, solvents, and toxic wastes buried in the ground can leach into the surrounding aquifer and contaminate the water. Pesticides and septic tanks can leach pollutants into the groundwater as well. Naturally occurring pollutants, such as boron, chromium and arsenic are not harmful in trace amounts, but in higher concentrations, they can be toxic.

    Contaminated groundwater can pose serious health effects to the more than 50% of the country's population who depend on groundwater as their source of drinking water. It is important that wells be tested for the presence of chemicals which could be dangerous. If wells are contaminated, it is equally important that they be rehabilitated if possible, or abandoned and properly destructed. Federal, state and local laws designed to protect groundwater sources are part of the solution as well.