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Improving Drinking Water Well ConditionWell Location • Well Construction • Well Management and Maintenance • New Wells • Abandoned Wells Well location is very important for avoiding drinking water contamination. A well's location is crucial whether it taps water from just below the ground surface or from several feet deep. Locating a well in a safe place takes careful planning and consideration of factors like the flow of surface water and groundwater. A well downhill from a livestock yard, a leaking tank, or a failing septic system can have a greater risk of contamination than a well located uphill 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 is often in the same direction as surface water flow. If the aquifer supplying water to your farmstead well is deep below the surface, its slope is probably different than that of the land surface. Separation distances Most states encourage good well location by requiring minimum separation distances from potential pollution sources, thus using the natural protection provided by soil. However, state well codes may not mention all farmstead activities and structures. Arkansas private well regulations (Arkansas Water Well Construction Code) do not specifically address pesticide mixing, storage of pesticides and fertilizers not contained in tanks, vehicle maintenance areas, and farm waste disposal sites. The Arkansas Department of Health is considering requiring written approval from them if chemical storage or disposal facilities are to be located within 100 feet of a well. When distances are not specified, provide as much separation as possible between your well and any potential contamination source. Separation distances are especially important if your farmstead is on highly permeable soils like sand and gravel or thin soil overlying 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 whenever possible. Soil and slope conditions can make selecting a well location tricky business. Keep in mind that separation distances required by the state are minimums, and you may choose greater separation distances depending on factors at your site. This will help provide reasonable assurance that your well will not be polluted by farmstead activities in the future. Also consider possible contamination sources on adjacent properties. Changing the location of your well in relation to contamination sources may protect your water supply, but not the groundwater itself. Any condition likely to cause groundwater contamination should be addressed, even if your well is far away from the potential source. Groundwater contamination is a violation of Arkansas law, even if the drinking water is not immediately affected. Simply separating your well from a contamination source may reduce the chance of pollution, but it does not guarantee that the well will be safe. Stormwater and groundwater can carry bacteria, nitrates, oil products, and pesticides from one place to another. Wells located in the path of polluted water may be contaminated by surface water washing into an improperly sealed well. Some wells may become contaminated through polluted recharge at great distances, depending on the depth of the aquifer and the well intake.
Poor well design can allow groundwater contamination by allowing surface water to reach the water table without filtering through soil. Wells located in pits, or constructed without grout or a cap, can allow surface water to carry bacteria, nitrates, pesticides, fertilizer, or oil products into the drinking water supply. Proper well design and construction reduce pollution risk by sealing the well from anything that might enter it from the surface. Even if the well is properly designed, the way in which it is constructed determines its ability to keep out contaminants. Several things that should be checked are described in the following sections. Well construction information may be available from the person who drilled your well or from the previous owner. If the well driller filed a well construction report, the Arkansas Water Well Construction Commission (AWWCC) or Arkansas Geological Commission (AGC) can attempt to locate the construction report for a small fee. 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. The AWWCC can help interpret construction requirements of the Arkansas well construction code. Casing and well cap The well driller installs a steel or plastic casing pipe during construction to prevent collapse of the borehole. The space between the casing and the sides of the hole provides a direct channel for surface water (and pollutants) to reach the water table. To seal off this channel, the driller fills the space with a cement or bentonite clay grout. The grout and casing prevent pollutants from seeping into the well. You can visually inspect your well casing for holes or cracks at the surface or down the inside of the casing with a light. If you can move the casing around by pushing against it, you definitely have a problem with your well's ability to keep out contaminants. In areas where fractured bedrock is less than 20 feet from the soil surface, you can check the well casing by listening for water running down into the well when the pump is not running. If you hear water, there could be a crack or hole in the casing, or the well may not be cased down to the water level. Either situation is risky. To prevent contaminants from flowing into the top of the well casing, the driller installs a tight-fitting, tamper-resistant, vermin-proof well cap to prevent the entry of insects, small animals, or surface water. The cap should be firmly installed and include a screened vent so that air can enter the well. Vents should face the ground, be tightly connected to the well cap or seal, and properly screened to keep insects out. The well cap should be checked periodically to see that it's in place and tightly secured. The well code requires a vermin-proof cap or seal for all private wells. Some wells may have pumping equipment attached to the well casing at the soil surface and a cap is not required because the equipment serves as a seal. Casing depth and height The depth of casing required by the state private well code depends on the nature of the subsurface geologic materials. Minimum requirements for unconsolidated formation wells (sand and gravel) are that casing should extend the full depth of the drill hole. For bedrock wells, casing should extend to a minimum depth of 10 feet below ground surface, and a minimum of one foot into the consolidated formation. The AWWCC can advise you on these minimum requirements. Meeting well code minimums does not, however, guarantee a safe water supply; you may want to exceed minimum casing depth requirements. Wells cased below the water level can afford greater protection from contamination. Well casing extending at least 30 feet below the water level can ensure that surface water is filtered through soil and geologic materials before entering the well. Typically, the casing extends one to two feet above surrounding land, preventing surface water from running down the casing or on top of the cap and into the well. The private well code requires that at least 8 inches of casing pipe extend above the final grade of the land. Well age Well age is an important factor in predicting the likelihood of high nitrate concentrations. A well constructed prior to 1930 is likely to be a shallower well located at the center of the farmstead and is probably surrounded by many potential contamination sources. Older wells can also have thinner, deteriorated casing that is corroded. Even newer wells (30 to 40 years old) with modern casing are subject to corrosion and deterioration. Older well pumps are more likely to leak lubricating oils into the well. If you have an older well, you may want to have it inspected by a qualified well driller or contact the AWWCC. Well type Dug wells pose the highest risk of allowing drinking water supply contamination because they are shallow and often poorly protected from surface water. A dug well is a large-diameter hole (usually more than 2 feet wide), which is often constructed by hand. Driven-point (sand point) wells, which pose a moderate to high risk, are constructed by driving assembled lengths of pipe into the ground. These wells are normally smaller in diameter (2 inches or less) and less than 50 feet deep. They can only be installed in areas of relatively loose soils, such as sand. Drilled wells cover all other types of wells, including those constructed by a combination of jetting and driving. Drilled wells for farmstead use are commonly 4 to 8 inches in diameter and when properly constructed pose a relatively low risk to groundwater. Well depth Shallow wells draw from the groundwater nearest the land surface, which may be directly affected by farmstead activities. Depending on how deeply the well casing extends below the water table, rain and surface water soak into the soil and may carry pollutants with it. Local geologic conditions determine how long it takes for this to happen. In some places, this process happens quickly, in weeks, days or even hours. Areas with thin soil over fractured bedrock or sand and gravel aquifers are particularly vulnerable. Even thick sands over fractured bedrock represent a site vulnerable to contamination. On the other hand, thick clay soils don't allow contaminants to reach the water table as quickly. They may prevent contamination or delay the day when a well "turns bad." If you have a deep well (more than several hundred feet below the water table), the groundwater supplying your well may have traveled a considerable distance underground over a long time, offering greater protection to the well. 3. Managing and maintaining existing wells You wouldn't let a tractor run too long without an oil change. Your well deserves the same attention. Good maintenance includes periodically testing the water, keeping the well area clean and accessible, keeping pollutants as far away as possible, and having a qualified well driller or pump installer check the well if problems are suspected. Better management of your existing well Existing wells were most likely located according to traditional practice or regulations in place at the time of construction. While these wells are still legal, you may want to consider how it conforms to current standards, which incorporate new knowledge about groundwater contamination and well water. These standards can be found in the state private well regulations available from the AWWCC. You might want to move such activities as pesticide mixing, tank rinsing, or gasoline storage further from your well and upgrade or better manage your septic system. You might want to upgrade wells, get rid of well pits, install caps, or extend casings. Changing the location of some farmstead practices may be prohibitive. Until you can meet minimum separation distance requirements, you should practice best management to control contaminants. If your livestock yard is too close to your well, for example, you may want to install a system for collecting runoff. You could install earthberms or concrete curbs to direct livestock yard runoff away from the well. Short-term manure stacks are another example. They pose a risk of well contamination by bacteria or nitrates. Locate them on clay soil or, better yet, a concrete slab to reduce the chance of polluting your drinking water. Also, protect them from rain. Backflow prevention Backflow, or backsiphonage, from pesticide mixing tanks allows chemicals to flow back into the well through the hose. Use an anti-backflow device when filling pesticide sprayer tanks to prevent the chemical mixture from flowing back into the well and contaminating groundwater. Inexpensive anti-backflow devices for hoses used to fill farm sprayers are available from irrigation or spray equipment suppliers. If you don't have such a device, keep the hose out of the tank when filling the pesticide sprayer. Arkansas Water Well Construction Code requires backsiphoning devices on all pumps used in conjunction with chemigation the injection of chemicals into irrigation water. Consider purchasing an inexpensive plastic nurse tank. A nurse tank is filled with water at the well and then used to fill the sprayer away from the farmstead and away from the well. (For more information about preventing well contamination from pesticide mixing and loading practices, see Work Sheet and Fact Sheet #2, Pesticide Storage and Handling.) You should also consider anti-backflow devices on all faucets with hose connections or maintain air gaps between hoses or faucets and the water level. Otherwise, water from laundry tubs, sinks, washing machines, pressure washers, outside hydrants, and swimming pools could flow back through plumbing to contaminate your water supply. Water supplies that have cross-connections between them (connections between two otherwise separate pipe systems, such as potable and non-potable) also put your drinking water at risk. Water testing Keep an eye on water quality in existing wells by testing it annually. Although you cannot have your water tested for every possible pollutant, some basic tests can indicate whether or not other problems exist. It is recommended to test your water annually for bacteria and nitrate. Where the well draws from sandy materials or granite bedrock, testing once for aggressiveness or corrosivity is also important. A good initial set of tests for a private well also includes hardness, alkalinity, pH, iron, manganese, sodium, conductivity, and chloride. In addition, you may choose to obtain a broad scan of your water quality for a number of contaminants. Some labs offer a screening for metals, inorganic chemicals, volatile organic chemicals, herbicides/pesticides, and coliform bacteria. The tests should include contaminants that could be near your farm like the most commonly used pesticides in your area. Test for lead if you have lead pipes or soldered copper joints. Test for volatile organic chemicals (VOCs) if there has been a nearby use or spill of oil, petroleum, or solvent. While testing for pesticides can be very expensive (often $80-$100 per compound analyzed), the expense may be justified if:
You should test your water more frequently than once a year if:
You can seek further advice on appropriate tests to run from your county Extension office, health department, or the AWWCC. You can have your water tested by both public and private laboratories. A list of currently approved laboratories can be obtained from the Arkansas Department of Health. Follow the lab's instructions for water sampling to assure accuracy of results. Use only the container provided and return samples promptly. Bacteria sample bottles are sterile and must be returned within specified time limits. Bacteria and nitrates are two important indicators. At excessive levels, they can cause health problems themselves and also may suggest problems with the well's location or construction. Hardness and pH indicate how corrosive the water may be to your plumbing system. Because many materials, including bacteria and nitrate-nitrogen, occur naturally in minor amounts in groundwater or can vary seasonally, you may want to contact a specialist for help in interpreting test results. Keep in mind that activities off your farm can affect your groundwater. Chemical spills, changes in land use, and the presence of landfills can increase the chance of pollutants getting into your water. If your water has a high nitrate or bacteria level, you may want to talk with a specialist about the need for additional testing. It is also important to record test results and to note changes in water quality over time. In addition to water analysis test results, you should keep records of a few other things to determine what is happening with your water system. These records should include well construction details and dates and results of well and pump maintenance. Well maintenance Well equipment doesn't last forever. Every 10 to 20 years, your well may require mechanical attention from a qualified well driller or pump installer. Follow these additional maintenance practices:
4. New wells New wells are expensive but they are a good investment for the future. Getting the most from such an investment means locating the well away from contamination sources and working to maintain the quality of the well. Some simple principles:
Many farmsteads have abandoned or unused wells. Old home sites with shallow wells are common, and no one knows how many of these wells there are in Arkansas. Pipes sticking out of the ground around the farmstead or in an area where a farmstead used to be or under an old windmill are the most obvious places for finding unused wells. You may not know the history of your property, however, and unused well locations may not be obvious. A depression in the ground may indicate an old well. Also, wells were often drilled in basements of houses, or under front steps, or near old cisterns. If not properly filled and sealed, these wells can provide a direct route for surface water to enter the groundwater without filtering through soil, or allow contaminant movement from one aquifer to another. In addition to these wells being a threat to groundwater, large open wells pose safety hazards for small children and animals. A licensed, registered well driller or pump installer should be hired to close these wells, since effective well plugging calls for experience with well construction materials and methods, as well as a working knowledge of the geology of the well site. You may, however, do your own well abandonment work. A license is not required, but you must meet the minimum well code requirements when you abandon and fill a well. Special equipment is often required to remove old pumps and piping and to properly install sealing material inside the well. Use of inappropriate materials and methods can lead to well settling, collapse, and continued groundwater contamination. If plugging materials are improperly installed in a well, patching up defective work is nearly impossible. State well regulations require reports of well plugging. These regulations also explain the following well-closing requirements:
Proper well closing takes time and money. Costs will vary with the well
depth, diameter, and geology of the area. Plugging an unused well near your home
removes a safety risk and may prevent contamination of your drinking water.
Contact the AWWCC for additional information and well closure report forms. |
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