Several problems associated with improperly constructed wells can result in groundwater contamination from the introduction of contaminated surface or groundwater. Types of wells that are a source of potential groundwater contamination include:

• Sumps and dry wells, which collect stormwater runoff and spilled liquids and are used for disposal. These wells sometimes contain contaminants such as used oil and antifreeze that may discharge into water supply areas.
• Drainage wells, which are used in wet areas to remove some of the water and transport it to deeper soils. These wells may contain agricultural chemicals and bacteria (U.S. EPA, 1990a).
• Injection wells, which are commonly used to dispose of hazardous and non-hazardous industrial wastes. These wells can range from a depth of several hundred to several thousand feet. If properly designed and used, these wells can effectively dispose of wastes. But undesirable wastes can be introduced into groundwater from injection wells when the well is located directly in an aquifer, or if leakage of contaminants occurs from the well head or casing or through fractures in the surrounding rock formations (U.S. EPA, 1990a).
• Improperly abandoned wells act as a conduit through which contaminants can reach an aquifer if the well casing has been removed, as is often done, or if the casing is corroded. In addition, some people use abandoned wells to dispose of wastes such as used motor oil. These wells may reach into an aquifer that serves drinking water supply wells. Abandoned exploratory wells (e.g., for gas, oil, coal) or test hole wells are usually uncovered and are a potential conduit for contaminants.
• Active drinking water supply wells that are poorly constructed can result in groundwater contamination. Construction problems, such as faulty casings, inadequate covers or lack of concrete pads, allow outside water and any accompanying contaminants to flow into the well. Sources of such contamination can be surface runoff or wastes from farm animals or septic systems. Contaminated fill packed around a well can also degrade well water quality. Well construction problems are more likely to occur in older wells that were in place prior to the establishment of well construction standards and in domestic and livestock wells.
• Poorly constructed irrigation wells also can allow contaminants to enter groundwater. Often pesticides and fertilizers are applied in the immediate vicinity of wells on agricultural land.

DEP has developed a web page on private well construction, which can be found at http://www.dep.state.pa.us/ (directLINK "wells").

This web page provides information on guidelines for well construction and abandonment, how to obtain information about your local conditions as well as information on Pennsylvania’s water well program.  You can also access EPA’s website that discusses private drinking water wells at http://www.epa.gov/OGWDW/pwells1.html.