EPA illustration of ground water pollutionGuide to Drinking Water Contamination
What is Groundwater and How Does It Become Polluted

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Water well pollution: water contaminant sources, water pollutant testing & detection,& water contaminant removal or treatment:

A guide to contaminants in drinking water from household wells: this article describes the sources of contaminants found in well water, well water testing strategies, and procedures for correcting drinking water well contamination problems.

We begin with an EPA definition of ground water and an explanation of ways in which groundwater becomes contaminated. The EPA information is expanded, illustrated, and linked to related in-depth information about drinking water and irrigation water safety, sources, contamination, and contamination tests or treatments to make water safe to drink or "potable".

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A Guide to Contaminants in Drinking Water from Household Wells

Tracking down well water contamination (C) Daniel Friedman- Original source: EPA Guide to Contaminants in Drinking Water from Household Wells - EPA 816-K-02-003 January 2002, expanded, illustrated and annotated with information from additional SOURCES, February 2013-May 2015

This article series provides general information about drinking water from home wells (also considered private drinking water sources).

It describes types of activities in your area that can create threats to your water supply.This document also describes problems to look for and offers maintenance suggestions.

Sources for more information and help are also listed.

Article series contents


An original US EPA document was annotated, edited for clarity, expanded, and illustrated. We also add links to greater detail. As just one example, where the original document noted that the distance from a well to possible sources of contamination are important, we add WELL CLEARANCE DISTANCES. Initial document ource: EPA 816-K-02-003 January 2002, updated here through February 2013. [1]

All of us need clean water to drink. We can go for weeks without food, but only days without water. Contaminated water can be a threat to anyone's health, but especially to young children.

About 15 percent of Americans have their own sources of drinking water, such as wells, cisterns, and springs. Unlike public drinking water systems serving many people, they do not have experts regularly checking the water's source and its quality before it is sent through pipes to the community.

To help protect families with their own wells, almost all states license or register water-well installers. Most also have construction standards for home wells. In addition, some city and county health departments have local rules and permitting.

All this helps make sure the well is built properly. But what about checking to see that it is working correctly and the water is always healthy to drink? That is the job of the well owner, and it takes some work and some knowledge.

This article series also answers the question: Who is responsible for making sure that the drinking water from a private well is safe?

What Is Ground Water And How Can It Be Polluted?

Ground water is a resource found under the earth's surface. Most ground water comes from rain and melting snow soaking into the ground. Water fills the spaces between rocks and soils, making an "aquifer". (See Watershed Graphic.) About half of our nation's drinking water comes from ground water. Most is supplied through public drinking water systems. But many families rely on private, household wells and use ground water as their source of fresh water.

Ground water - its depth from the surface, quality for drinking water, and chance of being polluted - varies from place to place. Generally, the deeper the well, the better the ground water. The amount of new water flowing into the area also affects ground water quality.

Ground water may contain some natural impurities or contaminants, even with no human activity or pollution. Natural contaminants can come from many conditions in the watershed or in the ground.

Water moving through underground rocks and soils may pick up magnesium, calcium and chlorides. Some ground water naturally contains dissolved elements such as arsenic, boron, selenium, or radon, a gas formed by the natural breakdown of radioactive uranium in soil. Whether these natural contaminants are health problems depends on the amount of the substance present.

Definition of watershed:

A "watershed" is the land area where water soaks through the earth filling an underground water supply or aquifer. It is also called a recharge area.

Definition of water table:

The "water table" is the line below which the ground is saturated or filled with water and available for pumping. The water table will fall during dry seasons. A well can pump water from either the saturated zone or an aquifer. Wells must be deep enough to remain in the saturated zone.

List of common sources of ground water [or well water] contamination

In addition to natural contaminants, ground water is often polluted by human activities such as

These problems are discussed in greater detail later in this article series.

Suburban growth is bringing businesses, factories and industry (and potential sources of pollution) into once rural areas where families often rely on household wells. Growth is also pushing new home developments onto the edge of rural and agricultural areas.

Often municipal water and sewer lines do not extend to these areas. Many new houses rely on wells and septic tanks. But the people buying them may not have any experience using these systems.

Is groundwater safe to drink?

Most U.S. ground water is safe for human use. However, ground water contamination has been found in all 50 states, so well owners have reason to be vigilant in protecting their water supplies. Well owners need to be aware of potential health problems. They need to test their water regularly and maintain their wells to safeguard their families' drinking water.

What is the Hydrologic Cycle?

The hydrologic cycle is the natural process of rain and snow falling to earth and evaporating back to form clouds and fall again.

The water falling to earth flows into streams, rivers, lakes and into the soil collecting to form ground water.

This EPA pamphlet, annotated & expanded in this article series, helps answer these questions.

It gives you general information about drinking water from home wells (also considered private drinking water sources). It describes types of activities in your area that can create threats to your water supply

. It also describes problems to look for and offers maintenance suggestions. Sources for more information and help are also listed.

[Editing for clarity by DF are marked by brackets or italics] Initial Source: EPA 816-K-02-003 January 2002


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