University of Missouri Extension

WQ676, New October 1995

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:

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:

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:

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.

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

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

Health and safety information on chemicals

Plans and recommendations for pesticide mixing and loading pads

Secondary containment regulations

Pesticide spills

Proper disposal of soil contaminated by a pesticide spill

Your local MU Extension center or regional DNR office:

What to read about

Groundwater and pesticides in groundwater

Health effects

Pesticide handling and management


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.
WQ676 Reducing the Risk of Groundwater Contamination by Improving Pesticide Storage and Handling | University of Missouri Extension

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