Assessing the Risk of Groundwater Contamination from

Pesticide Storage and Handling

Worksheet 2

Pesticides play an important role in agriculture. They protect crop yields and enable farmers to manage more acres with less labor. If pesticides are not handled carefully around the rural homestead, they can seep through the ground after a leak or spill, or they can enter a well directly during mixing and loading. The responsible use of pesticides by farmers will help assure the availability of safe groundwater for everyone.

Pesticides work by interfering with the life processes of plants, disease organisms, insects, and rodents. Many pesticides are also potentially toxic to people. Pesticides include herbicides, fungicides, insecticides, and rodenticides. If pesticides enter a water supply in large quantities, as can happen with spills or backsiphonage accidents, acute health effects (toxic effects apparent after only a single exposure) are possible. Effects will vary, depending on the toxicity of the pesticide and the amount of exposure. Using groundwater with low levels of contaminants 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 pesticides are found in water supplies, they are rarely present in high enough concentrations to cause acute health effects, which can include chemical burns, nausea, and convulsions. Instead, they typically occur at trace levels, and the concern is primarily their potential to cause chronic health problems from prolonged exposure.

Follow appropriate management procedures to greatly reduce the possibility of your drinking water being contaminated. Handle and dispose of pesticides properly to avoid risking contamination that could affect the water supplies and health of others.

The goal of Home·A·Syst is to help you protect the groundwater that supplies your drinking water.

• It will take you step-by-step through your pesticide storage, handling, 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 storage, handling, 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.

These terms may help you make more accurate assessments when completing worksheet 2. They may also help clarify some of the terms used in fact sheet 2.

Air gap: An air space (open space) between the fill hose and the spray tank 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 the unwanted reverse flow of liquids back down a water supply pipe into a well.

Backflow: The unwanted reverse flow of liquids in a piping system.

Backflow prevention device: (See anti-backflow device.)

Backsiphonage: Backflow caused by formation of a vacuum in a water supply pipe.

Closed handling system: A system for transferring pesticides or fertilizers directly from container to application equipment that minimizes the chance of exposure to handler or environment.

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.

Micrograms per liter (ug/L): The weight of a substance measured in micrograms contained in one liter. It is equivalent to 1 part per billion in liquid measure.

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 liquid measure.

Parts per billion (ppb): A measurement of concentration of one unit of material dispersed in one billion total units.

Parts per million (ppm): A measurement of concentration of one unit of material dispersed in one million total units.

Pesticide: A substance used as a management tool to control a plant disease, insect, or weed. Pesticides include herbicides, fungicides, insecticides, and rodenticides.

Rinsate: Rinse water from cleaning pesticide or fertilizer container.

Secondary containment: Impermeable floor and walls around a chemical storage area that allow pesticide recovery and minimize the amount of chemical seeping into the ground in case of a spill or leak.

Wash water: Solution containing very low concentrations of chemicals resulting from cleaning application equipment.

Step 1: In the table below, summarize your risk scores by checking the appropriate box for each risk category you answered on this worksheet.

Step 2: Look at your rankings for individual activities.

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

Any practices in shaded areas should be carefully reviewed. Some concerns you can take care of right away; others could be major or costly projects, requiring planning and prioritizing before you take action. The long-term goal of the Home·A·Syst program is to improve homestead practices and structures, so that they are classed as low risk. Activities classed as low risk generally reflect best management practices.

Transfer any activities that you ranked in the shaded areas in step 1 to the "High-Risk Activities" table on pages 2-3 of worksheet 12.

Step 3: Read fact sheet 2, Improving Pesticide Storage and Handling, if you haven't already. Consider how you might modify your homestead practices to better protect your drinking water.

The Homestead Assessment System is a cooperative project of Washington State University Cooperative Extension, Washington Department of Ecology, and the U.S. Environmental Protection Agency Region X.

Home·A·Syst team members: Christopher F. Feise and Edward B. Adams, WSU Cooperative Extension Water Quality Coordinators; James D. LaSpina, Homestead Assessment System Project Associate.

Pesticide Storage & Handling Technical Reviewers: Roland Schirman, WSU Cooperative Extension; Wes Sieg, Washington Association of Wheat Growers; Gary Thomasson, WSU Cooperative Extension; Joe Hoffman, Washington State Department of Agriculture; Jim Lassen, Wilbur-Ellis.

Adapted for Washington from material developed by the Wisconsin, Minnesota, and Kansas Extension Services and Farm·A·Syst Programs. Washington Home·A·Syst development was supported by the National Farmstead Assessment Program.

Information derived from Home·A·Syst worksheets is intended only to provide general information and recommendations to rural dwellers regarding their own homestead practices. It is not the intent of this educational program to keep records of individual results.