HOW SHOULD A WELL BE CONSTRUCTED TO REDUCE THE LIKELIHOOD OF CONTAMINATION FROM A SEPTIC SYSTEM?

Whether a well taps water just below the ground or hundreds of feet deep, its location on top of the ground is a crucial safety factor. Locating a well in a safe place takes careful planning and considering factors such as where the well is in relation to surface drainage and groundwater flow. A well downhill from a livestock yard, a leaking tank or a septic system runs a greater risk of contamination than a well on the uphill side of these pollution sources. Surface slope does not always indicate the direction a pollutant might flow once it gets into the ground. In shallow aquifers, groundwater flow often is in the same direction as surface-water flow.

If the aquifer supplying water to your farmstead well is deep below the surface, however, its slope may be different than that of the land surface. Finding out about groundwater movement on your farm may require special monitoring equipment. Many states encourage appropriate well location by requiring minimum separation distances from sources of potential pollution, thus using the natural protection provided by soil. However, state well codes may not mention some farmstead activities and structures.

When no distances are specified, provide as much separation as possible between your well and any potential contamination source, especially if your farmstead is on highly permeable soils or thin soil overlying limestone bedrock or if the contamination source or activity presents a high risk of contamination. Minimum separation distances regulate new well installation. Existing wells are required by law only to meet separation requirements in effect at the time of well construction. Make every effort, however, to exceed old requirements, and strive to meet current regulations. Both soil and slope can make placing a well tricky business. Keep in mind that separation distances required by the state are minimums. You may choose greater separation distances in some cases, depending on factors at your site. This will assure you that your well will not be polluted by farmstead activities in the future. Also consider contamination sources on adjacent properties.

Poor well design can cause contaminated groundwater to enter the well by allowing rain or snow melt to reach the water table without filtering through soil. Wells located in pits, or without grout or a cap, allow surface water to carry bacteria, pesticides, fertilizer or oil products into your drinking-water supply. Proper well design reduces the risk of pollution by sealing the well from anything that might enter it from the surface

The way in which a well was constructed, even if the design is sound, affects its ability to keep out contaminants. Several things you should check are described in the following sections. Information about well construction may be available from the person who drilled your well, from the previous owner or from the well-construction report. Employees in the your state Division of Geology and Land Survey in can try to find the construction report for you. This overview of well construction and inspection can help you understand your drinking-water contamination-risk ranking. For more information, contact a registered well driller or pump installer. Your Department of Natural Resources (DNR) regional office can help interpret construction requirements.

According to well construction practices, it is recommended that well casings extend to a depth greater than 25 feet or 10 feet below the static water level in sand and gravel formations. In bedrock, a depth of 30 feet is recommended for sandstone and 40 feet for others. It is recommended that a well owner consult with the county health department or any other agency responsible for well drilling standards. For more information on well-head protection and well construction, contact the National Drinking Water Clearinghouse (800-624-8301, 304-293-4191).