Bacteria Presence in
Water Wells

As you may know, the federal Centers for Disease Control and Prevention (CDC) provided nine midwestern states with a combined total of $1 million to assess the impact of the 1993 flood on water quality in private household served by wells. In some states, samples were taken at households where the wells had been flooded, in addition to households where wells were not flooded. Some households from both sets were found to have high total coliform bacteria levels, and there were detections of E. coli b acteria in some samples taken at households served by private wells.

Members of the National Ground Water Association supply and their families drink and use the same water. Like many industries, the ground water industry has made great strides in utilizing new techniques and technologies with the intent of providing safe and adequate quantities of drinking water from wells. NGWA members are highly skilled professionals and their businesses are highly regulated. In many states, ground water contractors must meet rigid state licensing or registration requirements, in cluding continuing education. Also, the construction and services contractors provide often must meet strict state construction codes. Regulatory agencies in the state can confirm a contractor's compliance with regulations, as well as local requirements.

NGWA endorses the administration of a fair and equitable contractor licensing program that is properly enforced to assure increased protection for the homeowner who uses ground water as a drinking water source; a public that has confidence in the contractor as a licensed professional; the protection of the ground water resource through adherence to proper water well construction standards; and a minimum level of competence among water well contractors.

The National Ground Water Association (NGWA) further encourages contractors to obtain voluntary certification following a comprehensive examination. Consumers may call the National Ground Water Association at 1-614-898-7791 to confirm a contractor's NGWA certification.

To help you better understand this issue, NGWA has prepared this background summary of steps you can take to maintain protection around wells.

Bacteria are native in the water environment, as they are in other surfaces, including food. Some water-borne bacteria are harmless, while others have the potential to transmit disease. Some, over time, can cause water quality to deteriorate or cause damage to the water well system. Therefore, the presence of certain bacteria in a well water sample should be viewed as a need for further action to determine what remedial measures may be necessary.

New wells can operate for many years without showing signs of bacterial contamination, but there are no guarantees. An annual well maintenance check, including a bacterial test, is recommended. Drinking water should also be tested any time the water changes in taste, odor, or appearance, or anytime a well is serviced. Your state agency or ground water contractor may be able to provide you with a list of laboratories or you may check in the Yellow Pages under "Laboratories-Testing" for a laboratory th at is certified to test drinking water for bacteria. The person taking your sample should follow the microbiological examination water sample collection procedures outlined in Methods for the Examination of Water and Wastewater. These procedures require refrigeration of a properly drawn sample during shipment to the testing laboratory. Also, more than one sample from a given source will be necessary to determine water system quality.

It is not practical to test water directly for every illness-causing bacterium, virus, and protozoan, so the water is tested for a group of indicator bacteria, which measure the sanitary protection of the well and water system. This group of common bacteria, called the "total coliform group," is a good indicator of sanitary protection for two reasons. First, coliform bacteria do not themselves usually cause disease, but if they show up in a water test, they indicate that surface contamination may hav e entered the water, and therefore the water may be potentially unsatisfactory or unsafe. Waterborne infectious disease is caused by fecal contamination, and fecal contamination occurs on the ground surface (in the case of animal waste), or near the ground surface (in the case of septic systems and sewers). The second reason that coliform bacteria are good indicators is that they are killed by disinfection the same way that most disease-causing organisms are killed. With few exceptions, if a well is prop erly disinfected and the coliform bacteria disappear, disease-causing organisms have also been killed.

If tests indicate coliform bacteria are present, water used for drinking and culinary purposes should be boiled for three minutes at a full, rolling boil while the source of the bacteria is determined and remedial steps are taken. If E. coli bacteria are detected, all uses of the water should be immediately stopped and efforts be made to locate the source, as well as to remedy the problem.

Water systems found to have total coliform levels should be properly disinfected. Chlorine or other compounds approved by state or local regulatory agencies should be used as disinfectants. Unless the state or local law requires otherwise, the quantity of chlorine compounds used for disinfection should produce a minimum of 50 parts per million available chlorine in solution when mixed with the total volume of water in the well. Common forms of chlorine used to disinfect water systems are calcium hypo chlorite and sodium hypochlorite. While unscented liquid household bleach is often used as a well disinfectant, bleach manufacturers have told NGWA their products are not intended for this use.

A qualified ground water contractor will assure proper amounts of disinfecting chemicals are uniformly distributed for a proper amount of time throughout the entire water depth of the well and water system. Most properly constructed wells can be effectively disinfected using the appropriate techniques, but there are exceptions. If contaminated items have entered into an inadequately covered well, the well may have be physically bailed out with special equipment before disinfection will be successful. In some cases, openings or cracks may have developed in the upper part of the well casing because of damage or corrosion. In other cases, the soil and rock of the area may not be adequately filtering percolating water and surface bacteria may be traveling deeper than usual. In these instances, special measures will be necessary, possibly including well reconstruction or the construction of a new well. The water supply should always be tested again following disinfection. Your local ground water contrac tor can help. You can also contact your nearest public health office for advice.

There are a variety of treatment methods available, such as chlorination, filtration, ozone, ultra violet light, and others to assure a disinfected drinking water supply. Contact your ground water contractor, or a water treatment professional to determine which method may be best for you. You should also contact your local or state regulatory official to determine which water treatment methods are allowed to be used in your area.

Well caps, sanitary seals and other construction features should be periodically inspected and repaired, if necessary, by a qualified ground water contractor. Water systems should be properly disinfected following construction, repair and maintenance. Like other valuable property assets, wells should be regularly and properly maintained.

The National Ground Water Association believes the grouting (sealing around the outside) of water wells is an effective and necessary measure to protect public health and the quality of our ground water supplies. Requirements for the grouting of all water wells should be an integral part of a state's well construction code. Grouting involves the placement of impermeable material (such as cement or bentonite) in the space between the well casing and borehole wall.

Wells that have been physically damaged, or wells constructed prior to the adoption of well construction regulations, may be candidates for replacement. Repairing a well may not prove to be cost effective if the well was not constructed to current state standards. Examples of unsafe wells include old dug wells with leaking walls and rotten boards for covers, wells at the bottom of old frost pits that are susceptible to flooding, wells with holes corroded through the casing, and wells too close to con tamination sources such as sewers or septic systems.

One potential ground water contamination source is abandoned wells and boreholes that penetrate aquifers or breach a zone that provides a significant barrier to contaminant migration. NGWA believes that all abandoned wells and boreholes that penetrate aquifers or breach a zone that provides a significant barrier to contaminant migration should be decommissioned. By decommissioning, it is meant that such wells and boreholes must be properly abandoned with a grouting material so as to prevent any con tamination from entering, circulating within, or leaving such structures. In most instances decommissioning of wells and boreholes should be performed by a qualified ground water contractor.

Independent studies have found greater instances of bacteria contamination in old, dug wells rather than in wells constructed by drilling technology and completed with modern and approved construction materials and techniques. Additionally, wells completed in pits are particularly susceptible to flood contamination.