Photograph of  a loose, unsanitary well plumbing system exposed to surface water runoffr  © DJ Friedman Well Water Contamination Caused by Humans & Farm Animals

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What human activities are likely to produce contaminants that may enter drinking water wells?

Information is given about drinking water from home wells & types of activities in your area that can create threats to your water supply.

We have added suggested sources of well water contamination and links to in-depth information on most of these.

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What Human Activities Can Pollute Ground Water?

Photograph of  a loose, unsanitary well plumbing system exposed to surface water runoffr  © DJ FriedmanBacteria and Nitrates: as Sources of Water Contamination from septic tanks, barns, farm animals

These pollutants are found in human and animal wastes. Septic tanks can cause bacterial and nitrate pollution. So can large numbers of farm animals.

Both septic systems and animal manures must be carefully managed to prevent pollution. Sanitary landfills and garbage dumps are also sources. Children and some adults are at extra risk when exposed to water-born bacteria.

These include the elderly and people whose immune systems are weak due to AIDS or treatments for cancer. Fertilizers can add to nitrate problems. Nitrates cause a health threat in very young infants called "blue baby" syndrome. This condition disrupts oxygen flow in the blood.

More information on water contamiantion caused by humans: see

Concentrated Animal Feeding Operations (CAFOs): [as Sources of Water Contamination]

The number of CAFOs, often called "factory farms," is growing. On these farms thousands of animals are raised in a small space. The large amounts of animal wastes/manures from these farms can threaten water supplies. Strict and careful manure management is needed to prevent pathogen and nutrient problems. Salts from high levels of manures can also pollute ground water.

Heavy Metals: [as Sources of Water Contamination]

Activities such as mining and construction can release large amounts of heavy metals into nearby ground water sources. Some older fruit orchards may contain high levels of arsenic, once used as a pesticide. At high levels, these metals pose a health risk.

[More information on water contamiantion caused by humans: see


Fertilizers and Pesticides: [as Sources of Water Contamination]

Farmers use fertilizers and pesticides to promote growth and reduce insect damage. These products are also used on golf courses and suburban lawns and gardens.

The chemicals in these products may end up in ground water. Such pollution depends on the types and amounts of chemicals used and how they are applied. Local environmental conditions (soil types, seasonal snow and rainfall) also affect this pollution. Many fertilizers contain forms of nitrogen that can break down into harmful nitrates.

This could add to other sources of nitrates mentioned above. Some underground agricultural drainage systems collect fertilizers and pesticides. This polluted water can pose problems to ground water and local streams and rivers. In addition, chemicals used to treat buildings and homes for termites or other pests may also pose a threat. Again, the possibility of problems depends on the amount and kind of chemicals.

The types of soil and the amount of water moving through the soil also play a role.

[More information on water contamiantion caused by humans: see


Unidentified chemical drums discovered during a home inspection might indicate an environmental site contamination hazard.Industrial Products and Wastes: [as Sources of Water Contamination]

Many harmful chemicals are used widely in local business and industry. These can become drinking water pollutants if not well managed. The most common sources of such problems are:

[Our photo (left) shows chemical waste drums found at a building site. That observation raised a reasonable concern for local contaminant spillage and suggested further environmental testing. - DF]

Local Businesses: [as Sources of Water Contamination]

These include nearby factories, industrial plants, and even small businesses such as gas stations and dry cleaners.

All handle a variety of hazardous chemicals that need careful management. Spills and improper disposal of these chemicals or of industrial wastes can threaten ground water supplies.

Leaking Underground Tanks & Piping: [as Sources of Water Contamination]

Petroleum products, chemicals, and wastes stored in underground storage tanks and pipes may end up in the ground water. Tanks and piping leak if they are constructed or installed improperly. Steel tanks and piping corrode with age. Tanks are often found on farms. The possibility of leaking tanks is great on old, abandoned farm sites. Farm tanks are exempt from the EPA rules for petroleum and chemical tanks.

[More information on water contamiantion caused by humans: see


Landfills and Waste Dumps: [as Sources of Water Contamination]

Modern landfills are designed to contain any leaking liquids. But floods can carry them over the barriers. Older dumpsites may have a wide variety of pollutants that can seep into ground water.

Household Wastes: [as Sources of Water Contamination]

Improper disposal of many common products can pollute ground water. These include cleaning solvents, used motor oil, paints, and paint thinners. Even soaps and detergents can harm drinking water. These are often a problem from faulty septic tanks and septic leaching fields.

[More information on water contamiantion caused by humans: see


Lead & Copper: [as Sources of Water Contamination]

Household plumbing materials are the most common source of lead and copper in home drinking water. Corrosive water may cause metals in pipes or soldered joints to leach into your tap water. Your water's acidity or alkalinity (often measured as pH) greatly affects corrosion. Temperature and mineral content also affect how corrosive it is.

They are often used in pipes, solder, or plumbing fixtures. Lead can cause serious damage to the brain, kidneys, nervous system, and red blood cells. The age of plumbing materials - in particular, copper pipes soldered with lead - is also important. Even in relatively low amounts these metals can be harmful. EPA rules under the Safe Drinking Water Act limit lead in drinking water to 15 parts per billion. Since 1988 the Act only allows "lead free" pipe, solder, and flux in drinking water systems. The law covers both new installations and repairs of plumbing.

For more information on avoiding lead in drinking water, visit the EPA's Lead in Drinking Water website.

[More information on water contamiantion caused by humans: see


Water Treatment Chemicals: [as Sources of Water Contamination]

Photo of a home water softener system

Improper handling or storage of water-well treatment chemicals (disinfectants, corrosion inhibitors, etc.) close to your well can cause problems.

[More information on water contamiantion caused by humans: see


septic tank

Septic tanks are designed to have a "leach field" around them - an area where wastewater flows out of the tank. This wastewater can also move into the ground water.

See The Septic System Information Website - not an EPA website - for in-depth information about inspecting and testing septic systems.

Also see Septic Contamination in Buildings - not an EPA website - for in-depth information about testing and cleaning-up sewage contamination in buildings.


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