About 95 percent of this country's rural residents use groundwater to supply their drinking water and farmstead needs. Wells are designed to provide clean water. If improperly constructed and maintained, however, they can allow bacteria, pesticides, fertilizer or oil products to contaminate groundwater. These contaminants can put family and livestock health at risk.
There are documented cases of well contamination from farmstead activities near drinking water wells. The condition of your well and its proximity to contamination sources determine the risk it poses to the water you drink. For example, a cracked well casing allows bacteria, nitrates, oil and pesticides to enter the well more easily. A spill of pesticides being mixed and loaded right near the well could result in the contamination of your family's drinking water supply. Feedlots, animal yards, septic systems, fertilizer applications and waste storage areas could release large amounts of nitrate, contaminating your well.
Preventing well water contamination is very important. Once the groundwater supplying your well is contaminated, it is very difficult to clean up. The only options may be to treat the water, drill a new well, or obtain water from another source. A contaminated well can also affect your neighbors' wells, posing a serious health threat to your family and neighbors.
The goal of Farm*A*Syst is to help you protect the groundwater that supplies your drinking water.
How will this worksheet help me protect my drinking water?
- It will take you step by step through your drinking water well condition and management practices.
- It will rank your activities according to how they might affect the groundwater that provides your drinking water supplies.
- It will provide you with easy-to-understand rankings that will help you analyze the risk level of your drinking water well condition and management practices.
- It will help you determine which of your practices are reasonably safe and effective, and which practices might require modification to better protect your drinking water.
Abandoned well: An unused well that has been permanently closed according to New Mexico regulations.
Air gap: An air space (open space) between the hose or faucet and water level, representing one way to prevent backflow of liquids into a well or water supply.
Anti-backflow (anti-backsiphoning) device: A check valve or other mechanical device to prevent unwanted reverse flow of liquids back down a water supply pipe into a well.
Aquifer: Zone in which readily extractable water saturates the pores of the geologic formations.
Backflow: The unwanted reverse flow of liquids in a piping system.
Backsiphonage: Backflow caused by formation of a vacuum in a water supply pipe.
Casing: Steel or plastic pipe installed while drilling a well, to prevent collapse of the well bore hole and entrance of contaminants, and to allow placement of a pump or pumping equipment.
Cross-connection: A link or channel between pipes, wells, fixtures or tanks carrying contaminated water and those carrying potable (safe for drinking) water. Contaminated water, if at higher pressure, enters the potable water system.
Drilled wells: Wells not dug or driven, including those constructed by a combination of jetting or driving. These wells are normally 4 to 8 inches in diameter.
Driven-point (sand point) wells: Wells constructed by driving assembled lengths of pipe into the ground with percussion equipment or by hand. These wells are usually smaller in diameter (2 inches or less), less than 50 feet deep, and can be installed in areas of relatively loose soils, such as sand.
Dug wells: Large-diameter wells often constructed by hand.
Groundwater: Subsurface water in a zone of saturation.
Grout: Slurry of cement or clay used to seal the space between the outside of the well casing and the bore hole, or to seal an abandoned well.
Milligrams per liter (mg/l): The weight of a substance measured in milligrams contained in one liter. It is equivalent to 1 part per million in water measure.
Assessing the Risk of Groundwater Contamination from Drinking Water Well Condition
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The Farm*A*Syst Program is a cooperative program funded nationally by: USDA Cooperative State Research Education Service (CSREES), USDA Natural Resources Conservation Service (NRCS), and the US Environmental Protection Agency. This worksheet has been produced by the National Farm*A*Syst Office located at B142 Steenbock Library, 550 Babcock Drive, Madison, WI 53706-1293, Phone: (608) 262-0024. This worksheet is based on the original Wisconsin Farmstead Assessment Program. The principal author for this worksheet was Susan Jones, US EPA Region V, Water Division, and University of Wisconsin-Extension, Cooperative Extension. |
July 24, 1998
Dennis Hoffman, Project Leader
Steve Dagitz, Webmaster