Glossary   
Aquifer – An underground formation or group of formations in rocks and soils containing enough ground water to
supply wells and springs.

Backflow – A reverse flow in water pipes. A difference in water pressures pulls water from sources other than the well
into a home’s water system, for example waste water or flood water. Also called back siphonage.

Bacteria – Microscopic living organisms; some are helpful and some are harmful. “Good” bacteria aid in pollution
control by consuming and breaking down organic matter and other pollutants in septic systems, sewage, oil spills, and
soils. However, “bad” bacteria in soil, water, or air can cause human, animal, and plant health problems.

Confining layer – Layer of rock that keeps the ground water in the aquifer below it under pressure. This pressure
creates springs and helps supply water to wells.

Contaminant – Anything found in water (including microorganisms, minerals, chemicals, radionuclide's, etc.) which may
be harmful to human health.

Cross-connection – Any actual or potential connection between a drinking (potable) water supply and a source of
contamination.

Heavy metals – Metallic elements with high atomic weights, such as, mercury chromium cadmium, arsenic, and lead.
Even at low levels these metals can damage living things. They do not break down or decompose and tend to build up
in plants, animals, and people causing health concerns.

Leaching field – The entire area where many materials (including contaminants) dissolve in rain, snow melt, or
irrigation water and are filtered through the soil.

Microorganisms – Also called microbes. Very tiny life forms such as bacteria, algae, diatoms, parasites, plankton, and
fungi. Some can cause disease.

Nitrates – Plant nutrient and fertilizer that enters water supply sources from fertilizers, animal feed lots, manures,
sewage, septic systems, industrial waste waters, sanitary landfills, and garbage dumps.

Protozoa – One-celled animals, usually microscopic, that are larger and more complex than bacteria. May cause
disease.

Radon – A colorless, odorless naturally occurring radioactive gas formed by the breakdown or decay of radium or
uranium in soil or rocks like granite. Radon is fairly soluble in water, so well water may contain radon.

Radionuclide's – Distinct radioactive particles coming from both natural sources and human activities. Can be very
long lasting as soil or water pollutants.

Recharge area – The land area through or over which rainwater and other surface water soaks through the earth to
replenish an aquifer, lake, stream, river, or marsh. Also called a watershed.

Saturated zone – The underground area below the water table where all open spaces are filled with water. A well
placed in this zone will be able to pump ground water.

Unsaturated zone – The area above the ground water level or water table where soil pores are not fully saturated,
although some water may be present.

Viruses – Submicroscopic disease-causing organisms that grow only inside living cells.

Watershed – The land area that catches rain or snow and drains it into a local water body (such as a river, stream,
lake, marsh, or aquifer) and affects its flow, and the local water level. Also called a recharge area.

Water table – The upper level of the saturated zone. This level varies greatly in different parts of the country and also
varies seasonally depending on the amount of rain and snow melt.

Well cap – A tight-fitting, vermin-proof seal designed to prevent contaminants from flowing down inside of the well
casing.

Well casing – The tubular lining of a well. Also a steel or plastic pipe installed during construction to prevent collapse of
the well hole.

Wellhead – The top of a structure built over a well. Term also used for the source of a well or stream.
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Utility Management Group Ltd.
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