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New October 1995

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Contents

• Glossary

Related publications

• WQ651, Assessing and Reducing the Risk of Groundwater Contamination From Drinking-Water Well Condition
• WQ652, Assessing the Risk of Groundwater Contamination From Pesticide Storage and Handling
• WQ653, Assessing the Risk of Groundwater Contamination From Fertilizer Storage and Handling
• WQ654, Assessing the Risk of Groundwater Contamination From Petroleum Product Storage
• WQ655, Assessing the Risk of Groundwater Contamination From Hazardous-Waste Management
• WQ656, Assessing the Risk of Groundwater Contamination From Household Wastewater Treatment
• WQ657, Assessing the Risk of Groundwater Contamination From Animal Manure Management Facilities
• WQ658, Reducing the Risk of Groundwater Contamination by Site Evaluation
• WQ659, Assessing the Risk of Groundwater Contamination — Overall Farmstead Assessment
• WQ660, An Action Program for Safe Drinking Water
• WQ675, Reducing the Risk of Groundwater Contamination by Improving Drinking Water Well Conditions
• WQ676, Reducing the Risk of Groundwater Contamination by Improving Pesticide Storage and Handling
• WQ677, Reducing the Risk of Groundwater Contamination by Improving Fertilizer Storage and Handling
• WQ678, Reducing the Risk of Groundwater Contamination by Improving Petroleum Product Storage
• WQ679, Reducing the Risk of Groundwater Contamination by Improving Hazardous Waste Management
• WQ680, Reducing the Risk of Groundwater Contamination by Improving Household Wastewater Treatment
• WQ681, Reducing the Risk of Groundwater Contamination by Improving Animal Manure Management

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Assessing the Risk of Groundwater Contamination From Pesticide Storage and Handling

Farm•A•Syst: Farmstead Assessment System Worksheet #2

Included when you order this worksheet: MU publication WQ676, Reducing the Risk of Groundwater Contamination by Improving Pesticide Storage and Handling, the fact sheet that corresponds with this worksheet.

Table 1
Pesticide storage and handling: Assessing drinking-water contamination risk

¹Illegal for new well installation. Existing wells must meet separation requirements in effect at time of construction.
²Besides representing a higher-risk choice, this practice also violates Missouri law.

Why should I be concerned?

Pesticides are showing up where they're not wanted — in our drinking water. If pesticides are not handled carefully around the farmstead, they can seep through the ground after a leak or spill, or they can enter a well directly during mixing and loading.

Pesticides play an important role in agriculture. They have increased farm production, and they have enabled farmers to manage more acres with less labor.

Pesticides work by interfering with the life processes of plants and insects. Pesticides also may be toxic to people. If pesticides enter a water supply in large quantities — as can happen with spills or backsiphonage accidents — acute exposure (toxic effects apparent after only a short period of exposure) can range from moderate to severe, depending on the toxicity of the pesticide and the amount of exposure. Contaminated groundwater used for drinking-water supplies may result in chronic exposure (prolonged or repeated exposure to low doses of toxic substances), which may be hazardous to people and livestock.

When found in water supplies, pesticides normally are not present in high-enough concentrations to cause acute health effects, which can include chemical burns, nausea and convulsions. Instead, they typically occur in trace levels, and the concern is primarily for their potential for causing chronic health problems from prolonged exposure.

Your drinking water is least likely to be contaminated if you follow appropriate management procedures and properly dispose of wastes in a location that is off the farm site. However, proper offsite disposal practices are essential to avoid risking contamination that could affect the water supplies and health of others.

How will this worksheet help me protect my drinking water?

It will take you step by step through your pesticide handling, storage and disposal 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 pesticide handling, storage and disposal 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.

How do I complete the worksheet?

Follow the directions at the top of the next chart. It should take you about 15 to 30 minutes to complete this worksheet and figure out your ranking.

Pesticide Leachability Chart

¹The rating is an estimate, but reasonably accurate compared to estimated ratings footnoted with a ².
²The rating is a guess, and subject to a higher degree of error than estimates footnoted with a single asterisk.
Adapted from Becker, R.L., et al. 1990, Pesticides: Surface Runoff, Leaching, and Exposure Concerns. Minnesota Extension Service. Data were derived from U.S. Department of Agriculture SCS/ARS Pesticides Properties Data Base, Version 1.9, August 1989, developed by R.D. Wauchope et al., and ratings derived by D.W. Goss.
Chart modified annually. Contact your Natural Resources Conservation Service (NRCS) or local MU Extension center for the most recent version.

What do I do with these rankings?

Step 1
Begin by determining your overall well management risk ranking using Equation 1.

Total the rankings for the categories you completed, and divide by the number of categories you ranked:

Equation 1

¹Carry your answer out to one decimal place.

This ranking gives you an idea of how your well management practices as a whole might be affecting your drinking water. This ranking should serve only as a general guide, not a precise diagnosis. Because it represents an average of many individual rankings, it can mask any individual rankings (such as 1s or 2s) that should be of concern. (Step 2.)

Enter your well management risk ranking above in the first table in Worksheet #9 (MU publication WQ659). Later you will compare this risk ranking with other farmstead-management rankings. Worksheet #8 (MU publication WQ658) will help you identify your farmstead's site conditions (soil type, soil depth and bedrock characteristics), and Worksheet #9 (MU publication WQ659) will show you how these site conditions affect your risk rankings.

Step 2
Look over your rankings for individual activities:

• Low-risk practices (4s)
  ideal; should be your goal despite cost and effort
• Low- to moderate-risk practices (3s)
  provide reasonable groundwater protection
• Moderate- to high-risk practices (2s)
  inadequate protection in many circumstance
• High-risk practices (1s)
  inadequate; pose a high risk of polluting groundwater

Regardless of your overall risk ranking, any individual rankings of "1" require immediate attention. Some concerns you can take care of right away; others could be major — or costly — projects, requiring planning and prioritizing before you take action.

Find any activities that you identified as 1s and list them under "High-Risk Activities" in Worksheet #9 (MU publication WQ659).

Step 3
Read Fact Sheet #1 (MU publication WQ675), Improving Drinking-Water Well Conditions, and consider how you might modify your farmstead practices to better protect your drinking water.

Glossary

These terms may help you make more accurate assessments when completing Worksheet #1 (MU publication WQ651). They also may clarify some terms used in Fact Sheet #1 (MU publication WQ675).

• Abandoned water well
  A well that is permanently discontinued or that is in such disrepair that its continued use for obtaining groundwater is impractical or may be a health hazard.
• 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
  A water-bearing formation (soil or rock horizon) that transmits water in sufficient quantities to supply a water well.
• Bored wells
  Wells constructed using augers, scoops, drag lines or similar equipment. These holes are usually of large diameter and are constructed in alluvial or glacial material.
• Casing
  An impervious durable pipe placed in a well to prevent the walls from caving and to seal off surface drainage or undesirable water, gas or other fluids to prevent them from entering the well.
• 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 usually are 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
  A well in which the side walls may be supported by material other than standard weight steel casing. Water enters a dug well through the sides and bottom.
• Groundwater
  The water in the zone of saturation in which all of the pore spaces of the subsurface material are filled with water. The water that supplies springs and wells is groundwater.
• Grout
  Slurry of cement or bentonite clay used to seal the annular space between the outside of the well casing and the bore hole. Also used in sealing abandoned wells.
• Milligrams per liter (mg per liter)
  The weight of a substance measured in milligrams contained in 1 liter. It is equivalent to 1 part per million in water measure.
• Parts per million (ppm)
  A measurement of concentration of one unit of material dispersed in 1 million units of another.
• Pressure grout
  Refers to the process of applying grout material under pressure to the annular space of a well to seal it and thus prevent vertical movement of fluids through the annular space. Grout must be introduced from the bottom of the annular space.
• Water table
  The upper level of groundwater in a zone of saturation. Fluctuates with climatic conditions on land surface and with aquifer discharge and recharge rates.
• Well cap (seal)
  A method or device used to protect a well casing or water system from the entrance of any external pollutant at the point of entrance into the casing.

The Missouri Farmstead Assessment System is a cooperative project of MU Extension; College of Agriculture, Food and Natural Resources; and the Natural Resources Conservation Service.

The National Farmstead Assessment Program provided support for development of the Missouri program. These materials are adapted from the Wisconsin and Minnesota prototype versions of Farm•A•Syst.

This material is based upon work supported by the Extension Service, U.S. Department of Agriculture, under special project number 91-EHUA-1-0055 and 91-EWQI-1-9271.

Adapted for Missouri from material prepared by Susan Jones, U.S. E.P.A., Region V, Water Division, and University of Wisconsin Cooperative Extension.

MU Extension Farm•A•Syst team members: Joe Lear, Regional Agricultural Engineering Specialist and Chief Editor; Beverly Maltsberger, Regional Community Development Specialist; Robert Kelly and Charles Shay, Regional Agricultural Engineering Specialists; Thomas Yonke, Program Director, Agriculture and Natural Resources; Jerry Carpenter, State Water Quality Specialist; and Bob Broz, Water Quality Associate.

Technical review provided by August Timpe, Missouri Department of Natural Resources; Charles Fulhage, MU Department of Agricultural Engineering; U.S. E.P.A. Region VII, Environmental Sciences Division; and Missouri Natural Resources Conservation Service.

WQ652, new October 1995