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Reducing the Risk of Groundwater Contamination by Improving Pesticide Storage and Handling

Farm•A•Syst: Farmstead Assessment System Fact Sheet #2

This publication is included when you order MU publication WQ652, Assessing the Risk of Groundwater Contamination From Pesticide Storage and Handling, the worksheet that corresponds with this fact sheet.

In this publication, we'll examine five areas of pesticide management on your farmstead: pesticide storage practices, mixing and loading practices, spill cleanup, container disposal practices and other management practices.

When handling pesticides, wear proper protective clothing at all times. Personal protection is not addressed in Farm•A•Syst because its focus is groundwater and drinking-water protection. The Contacts and References section provides some safety information sources.

Pesticide storage practices

If stored safely in a secure location, pesticides pose little danger to groundwater. Common sense suggests keeping pesticides dry and out of the way of activities that might knock over a jug or rip open a bag. Short-term storage (during seasonal use) poses a lower risk than year-round storage, but any storage, regardless of how long, poses a risk to groundwater.

If a spill does occur, an impermeable (waterproof) floor, such as concrete, should eliminate any chemical seepage into the ground. Putting a curb around the floor will prevent chemicals from spreading to other areas.

Secondary containment provides an impermeable floor and walls around the storage area, which will minimize the amount of pesticide seeping into the ground if a bulk-liquid pesticide-storage tank leaks.

A mixing/loading pad provides for secondary containment during the transfer of pesticides to spraying equipment or nurse tanks.

Building a new storage facility

Building a new facility just for pesticide storage may be expensive, but generally it will be safer than trying to modify areas meant for other purposes.

When building a new facility, keep in mind a few principles of safe pesticide storage:

  • Place the building 300 feet away from your well. Make the distance greater if the site has sandy soils or fractured bedrock near the land surface. The risk of pesticide contamination of groundwater is influenced by properties of both the pesticide and the soil on which it is spilled or applied. (Pesticides, Surface Runoff, Leaching and Exposure Concerns, in the Contacts and References section, provide more information on these topics. Also, Worksheet #8 (MU publication WQ658, Site Evaluation), helps you in ranking your farmstead soils and geologic conditions according to their ability to keep pesticides and other contaminants out of groundwater.)
  • Contaminated surface water should drain to a properly designed storage facility and should be disposed of in a no-discharge manner.
  • The mixing and loading area should be close to your storage facility to minimize the distance that chemicals are carried.
  • The building foundation or secondary containment floor should be well drained and high above the water table. The subsoil should have a low permeability.
  • Provide pallets to keep large drums or bags off the floor. Shelves for smaller containers should have a lip to keep the containers from sliding off. Steel shelves are easier to clean than wood if a spill occurs. Store dry products above liquids to prevent wetting from spills.
  • If you plan to store large bulk tanks, provide a containment area large enough to confine 125 percent of the contents of the largest bulk container plus the displaced volume of any other storage tanks in the area.
  • A locked storage cabinet or building provides security. Preventing unauthorized use of pesticides reduces the chance of accidental spills. Provide signs or labels identifying the cabinet or building as a pesticide storage area. Labels on the outside of the building give firefighters information about pesticides during an emergency response for a fire or a spill.
  • Provide adequate road access for deliveries and emergency equipment.
  • Keep pesticides separate to prevent cross-contamination. Keep herbicides, insecticides and fungicides on separate shelves or in different areas.
  • For information on other factors to consider in the design of a storage facility — such as ventilation, water access, temperature control and worker safety — contact your local MU Extension center or the MU Department of Agricultural Engineering at 573-882-2731 for plans and recommendations.

Modifying an existing storage facility

Even if you decide to improve your current storage building, applying the above principles can be expensive. Compared to the cost of a major accident or a lawsuit, however, storage improvements are a bargain.

The cheapest alternative you may have is to cut back on the amounts and types of pesticides stored. If that's not practical, consider how you can protect the pesticides you keep in storage. Sound containers are your first defense against a spill or leak.

If a container is accidentally ripped open or knocked off a shelf, confine the spill to the immediate area and clean it up promptly. The building should have a solid floor and, for liquid pesticides, a curb. The secondary containment space should be large enough to hold 125 percent of the contents of the largest full container plus the displaced volume of any other storage tanks in the area.

Remodeling existing facilities that serve other uses may be less expensive than building a new facility, but remodeling can be complicated. When existing buildings must accommodate other activities, using them to store pesticides as well could compromise the safety of people and the environment. Storing chemicals in a separate facility reduces the risk associated with fire or accidental spills. Never store pesticides inside a wellhouse or a facility containing an abandoned well.

You can reduce damages by anticipating emergencies. Fires in a storage area present a special hazard to people and the environment. If containers are damaged, the stored chemicals may be carried away by water and spread over a large area.

Label windows and doors to alert firefighters to the presence of pesticides and other products stored in the structure. It's a good idea to keep a separate list of the chemicals and amounts stored. Keep a copy of the list in the house or away from the storage area, and provide a copy to local fire protection and the local emergency-response coordinator.

If a fire occurs, consider where the surface runoff water will go and where it might collect. For example, a curb around a floor can help confine contaminated water.

In making the storage area secure, also make it accessible, to allow getting chemicals out in a hurry.

Mixing and loading practices

Groundwater contamination can result even from small spills in the mixing and loading area. Small quantities spilled regularly in the same place can go unnoticed, but the chemicals can build up in the soil and eventually reach groundwater. By mixing and loading on an impermeable surface, such as concrete, you can contain and reuse most spilled pesticides.

A mixing and loading pad

Containing pesticide spills and leaks requires an impermeable surface for mixing and loading. The pad should be large enough to contain leaks from bulk tanks, wash water from cleaning equipment and spills from transferring chemicals to the sprayer or spreader (Figure 1).

The size of the pad also depends on the equipment you use. It should provide space for washing and rinsing around the parked equipment. Having several separate rinsate (rinse water) storage tanks allows you to keep rinsate from different chemicals separate. That way, it can be used as mixing water on subsequent loads.

Place the pad next to the storage area. Make sure that any water from the pad moves away from the well to an approved storage facility and is disposed of in a no-discharge manner.

If you are considering building a mixing and loading pad, contact your local MU Extension center or the MU Department of Agricultural Engineering for more information.

Farm-sized pesticide facility Figure 1
Farm-sized pesticide facility. Source: Farm-Sized Mixing/Loading Pad and Agri-chemical Storage Facility, by D.W. Kammel and D. O'Neil, presented at the American Society of Agricultural Engineers, June 24 to 27, 1990.

Better management on your existing mixing and loading site

Spills and leaks are bound to occur from time to time. Even if you don't have an impermeable mixing and loading pad, you can minimize contamination by following some basic guidelines:

  • Avoid mixing and loading pesticides near your well. One way to do this is to use a nurse tank to transport water to the mixing and loading site. Ideally, you should move the mixing site each year within the field of application.
  • Avoid mixing and loading on gravel driveways or other surfaces that allow spills to sink quickly through the soil. A clay surface is better than sand.
  • Install a backsiphon-prevention device on the well or hydrants to prevent reverse flow of liquids into the water supply. Never put the hose in the sprayer tank. Provide an air gap of 6 inches between the hose and the top of the sprayer tank.
  • Always supervise sprayer filling. A certified applicator must supervise operations for restricted-use pesticides.
  • Consider a closed handling system, which transfers the pesticide directly from storage container to applicator equipment (through a hose, for example). Humans and the environment are never inadvertently exposed to the pesticide.
  • Use rinsate for mixing subsequent loads. Spray the last rinsate load on the labeled crop.

Spill cleanup procedures

For dry spills, promptly sweep up and reuse the pesticide as it was intended. Dry spills are usually easy to clean up.

For liquid spills, recover as much of the spill as possible, and reuse as it was intended. It may be necessary to remove and field apply some contaminated soil.

The Missouri Clean Water Act (10 CSR 20 - 8.500) requires that spills of any amount to streams or lakes be reported. On the soil or on a mixing and loading pad, report concentrate spills greater than l quart, and dilute solutions greater than 5 gallons. Report spills of smaller quantities if they may cause damage because of the specific compound or spill location.

To report, call the 24-hour emergency hotline of the Missouri Department of Natural Resources at 573-634-2436.

Remove the spilled material and contaminated soil no matter what the quantity, and dispose of it according to recommendations you receive when you report the spill.

Have an emergency-response plan for the site. Know where the runoff water will go, how to handle your particular chemicals and whom to call for help.

Container disposal practices

Unwashed and improperly stored containers can lead to groundwater contamination by allowing chemical residues to leak onto the ground. Some basic guidelines can help avoid similar problems:

  • As often as possible, use returnable containers and minibulks, and take them back to the dealer.
  • Pressure-rinse or triple-rinse plastic containers immediately after use because residue can be difficult to remove after it dries. Pour rinse water into the spray tank. Puncture containers, and store them in a covered barrel until you can take them to a permitted landfill or recycling center.
  • Recycle plastic and metal containers whenever possible.
  • Shake out bags, bind or wrap them to minimize dust and take them to a permitted landfill.

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

(For more information about disposal of pesticide containers, refer to Worksheet #5 (MU publication WQ655) and Fact Sheet #5 (MU publication WQ679), Hazardous Waste Management. Fact Sheet #5 also discusses the risks of burning these containers.)

Other management practices

Reducing pesticide waste makes financial as well as environmental sense, but it means more than just reducing spills. It also means not buying more than you need to apply, keeping records of what you have on hand and using older products first.

  • Buying only what you need makes long-term storage unnecessary. You also avoid cold-weather problems, which can make some pesticides useless.
  • Record keeping may seem like a task unrelated to groundwater contamination, but knowing what you've used in the past and what you have on hand lets you make better purchasing decisions. Keep records of past field-application rates and their effectiveness. Along with field records, add information such as the manufacturer's name and address, chemical types and handling precautions. This information is important if you must respond quickly to an accident.
  • Using older products first keeps your inventory current and effective. Before using chemicals that have been stored for a few years, though, check with your local MU Extension specialist about possible restrictions on their use.

Atrazine at 40,000 parts per billion: A case example

Staff of Wisconsin's Department of Agriculture, Trade and Consumer Protection determined that careless disposal of atrazine containers might have contaminated the water supply of a dairy farm. The atrazine concentration in the well water was above the state groundwater standard of 3.5 micrograms per liter, or parts per billion (ppb). Upon visiting the farm, the staff found a box of empty 2.5-gallon liquid-atrazine containers discarded outside and beneath the drip line of a farm building. Concentrate residues were visible on the outside of the containers. Surface runoff from the livestock yard flowed past the containers, discharging near the well field. Samples of surface soil in the drainage way near the containers contained atrazine at a concentration of more than 40,000 ppb. Such disposal incidents greatly increase the likelihood of groundwater contamination.

Federal standard for Atrazine is 3 ppb.

Contacts and references

General pesticide information

  • National Pesticide Telecommunication Network
    Answered 24 hours a day, 365 days a year. Provides information on recognizing and treating pesticide poisoning; pesticide products, cleanup and disposal; contacts for animal poison centers; certification and training programs; and pesticide laws.

Health effects of pesticides in water

Division of Health and Bureau of Environmental Epidemiology, Jefferson City, Mo., 573-751-6102. With specific questions, contact your local MU Extension specialist, county health department or Natural Resources Conservation Service staff.

Drinking-water quality and treatment and health advisories

  • EPA safe drinking-water hotline

Health and safety information on chemicals

  • Chemical Referral Center, sponsored by the Chemical Manufacturers Association.
  • The center does not answer questions but does serve as a central contact point in non-emergency situations. You also can contact Chemtree

Plans and recommendations for pesticide mixing and loading pads

  • Your local MU Extension center or the MU Department of Agricultural Engineering

Secondary containment regulations

  • Missouri DNR Technical Assistance Program for Secondary Containment Regulations

Pesticide spills

  • The 24-hour emergency hotline of the Department of Natural Resource

Proper disposal of soil contaminated by a pesticide spill

Your local MU Extension center or regional DNR office:

  • Kansas City Regional Office
  • Macon Regional Office
  • Jefferson City Regional Office
  • St. Louis Regional Office
    Springfield Regional Office
  • Poplar Bluff Regional Office

What to read about

  • Publications are available from sources listed at the end of the reference section. (Refer to number in parentheses after each publication.)

Groundwater and pesticides in groundwater

  • Missouri's Hidden Waters. Missouri Department of Natural Resources, Rolla, Mo. (1)
  • Groundwater: An Economic Resource Worth Protecting. Missouri Department of Natural Resources, Rolla, Mo. (1)
  • How To Determine Groundwater Flow Direction. 1991. (4)

Health effects

  • The product label. Read your product labels carefully for specific information on pesticide health effects.
  • Pesticides: Surface Runoff, Leaching and Exposure Concerns. 1990. University of Minnesota Bulletin AGBU-3911. (4)
  • Pesticides and Groundwater: A Health Concern for the Midwest. 1986. Freshwater Foundation. (5)
  • Pesticides: Health Effects in Drinking Water. 1985. Cornell Cooperative Extension. (6)
  • Health Advisory Summaries. 1989. U.S. Environmental Protection Agency, Washington, D.C. (3) Specifies maximum acceptable levels of pesticide concentrations in drinking water and describes health effects that might be caused by particular pesticides in drinking water.

Pesticide handling and management

  • Fertilizer and Pesticide Containment Facilities Handbook. 1991. MWPS37. (8)
  • EPA Journal.
  • Pesticides: A Community Action Guide. 1985. Concern, Inc., Washington, D.C. (7)
  • Chemicals in Your Community: A Guide to Emergency Planning and Right To Know Act. 1988. (3) Contains information on implications of this law for farmers.
  • Citizen's Guide to Pesticides. 1989. (3) Free 24-page publication contains information on handling, storage and disposal of pesticides, reducing exposure to pesticides and what to do in a pesticide emergency. Also provides addresses and phone numbers for EPA regional pesticide offices and state pesticide agency contacts.


  • Your DNR regional office. (Listed in Who to Call).
  • U.S. EPA, Office of Pesticide Programs (TS-766C), 401 M Street S.W., Washington, D.C. 20460.
  • Minnesota Extension Service Distribution Center, 3 Coffey Hall, 1420 Eckles Ave., St. Paul, Minn. 55108-1030
  • Freshwater Foundation at Spring Hill Center, 725 County Road 6, Wayzata, Minn. 55391
  • Cornell Resource Center, PO Box 3884, Ithaca N.Y. 14852
  • Concern, Inc., 1794 Columbia Road N.W., Washington, D.C. 20009
  • Your local MU Extension center or the Midwest Plan Secretary, Agricultural Engineering Department, 205 Agricultural Engineering, Columbia, Mo. 65211
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.

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