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50 Ways Farmers Can Protect Their Groundwater
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38. Make Sure Your Well Is Constructed Properly

casing

Some problems with well construction are obvious, such as evidence of poor cementing or visible cracks in the casing. But quite often, not-so-obvious problems are responsible for your water-quality woes. Whether you are installing a new well or evaluating an existing one, look at four main areas: watertight casing; grout; watertight seals; and graded slope.

To keep surface water out of the well, the casing must extend at least 8 inches above the ground. If the area is prone to flooding, extend the casing 2 feet higher than the highest known flood level. If a well needs to extend through a shallow aquifer to reach deeper groundwater, be sure the casing extends below the level of the shallow aquifer.

watertight casing Also, be sure the casing around your well is constructed of proper materials. Steel pipe is used most often in small-diameter wells because it withstands stress during installation, pressure from surrounding earth, and corrosive soil and water. However, thermoplastic is becoming increasingly popular. If the soil is particularly corrosive, stainless steel may be used. For large, bored wells, the casing is sometimes made of concrete or fiberglass.
grout There is usually a gap between the wall of the drilled or bored well hole and the outside of the casing. Grout must be placed in this gap or surface contaminants will move right down the side of casing and into your groundwater. Also, all points where electrical wiring, pipes, or observation equipment enter the well should be properly sealed.
graded slope around the wellhead A graded slope around the wellhead directs surface water away from the immediate area of the well, decreasing the chances of contamination.
You must disinfect your well any time the system is opened You must disinfect your well any time the system is opened for repair or a new one is installed. Typically, the well contractor or pump installer is responsible for making sure this is done correctly.
inspect an existing well for proper construction When you inspect an existing well for proper construction, it helps if you have the well log—the record kept by the well driller. If neither you nor the well driller has the well log, check with the Illinois State Geological Survey or Illinois State Water Survey. Take the log to your local Department of Public Health, and they should be able to tell you if your well meets current construction standards.
types of wells Finally, when inspecting an existing well, it's important to consider the type of well you have. There are three major types—sand-point wells; large-diameter dug or bored wells; and deep-drilled wells.
Sand-point wells Sand-point wells are probably the most vulnerable to contamination because they are shallow—typically less than 40 feet deep. In addition, they are used in areas that have highly permeable sand and gravel aquifers. But they are not as widespread in the Midwest as the other two types of wells.
Large-diameter dug or bored wells Large-diameter dug or bored wells are also particularly vulnerable to contamination from sources near the well because of their design and generally shallow depth.
Deep-drilled wells Deep-drilled wells are often not considered vulnerable to contamination from nonpoint sources of pollution. However, evaluate the depth to the aquifer to get an idea of the risk. Also, a lot depends on the well's solid-steel casing, which keeps out shallow groundwater. If only a few feet of a deep well is cased, shallow groundwater may seep in. Shallow groundwater can carry contaminants.
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