How to Prevent Water Contamination

Crop and Soil Management Strategies

• Crop rotation, including cover crops; (maintain crop residues, enhance organic matter)
• Selection of suitable varieties including pest resistant varieties;
• Proper seed bed preparation and planting;
• Proper drainage and irrigation management;
• Proper equipment use to avoid soil compaction.

Conservation Buffers

Conservation buffers are areas designed to intercept and trap potential pollution before it reaches surface water. Often native grasses are planted alone or in combination with shrubs and trees along field borders between the crop and a waterway. Buffers trap pesticides, bacteria, fertilizers, and soil sediment reducing the amount of contaminants that move off the site. Buffers are one of the best management tools a landowner can install as they offer multiple benefits and require little in the way of maintenance.

Choose these sites for more information on conservation buffers:
http://conservationbuffers.unl.edu/bufferpubs.htm
http://www.ipm.iastate.edu/ipm/icm/2002/6-24-2002/buffers.html
http://www.ipm.iastate.edu/ipm/icm/2000/6-26-2000/consbuff.html
http://www.nrcs.usda.gov/feature/buffers/

Integrated Pest Management (IPM) and Best Management Practices to Reduce Risk

An IPM program combines the best techniques to keep pests below economically damaging threshold levels and potentially reduce the need for pesticides. When pesticide use is reduced or eliminated, the risk of surface or groundwater contamination is reduced or eliminated.

The IPM program can also facilitate the selection of a "low impact" pesticide to be delivered precisely on target and at the proper time. Crop scouting or monitoring correctly identifies the pest and collects information needed so that applications are made only when needed and only when the pest is vulnerable, allowing for a more effective pesticide application. Reducing the need for multiple applications of pesticides reduces the chance that pesticides may reach and contaminate water.

Visit any of these web sites to learn more about best management practices to protect water resources from agricultural pesticides:
http://www.owr.ehnr.state.nc.us/ref/20/19700.htm
http://www.csuextstore.com/store/pc/viewCategories.asp?idCategory=55 (must be ordered)
http://ohioline.osu.edu/aex-fact/0527.html
www.ecn.purdue.edu/SafeWater/Field/WQ_42.pdf
http://www.soil.ncsu.edu/publications/Soilfacts/AG-439-31/

Selecting Appropriate Pesticides

Protecting water from contamination requires planning and records. Past pest scouting or monitoring records along with past pesticide application records help you select the best controls. Selecting the proper pesticide for the crop, the pest, and the site is important. If the soils are vulnerable to leaching, a pesticide with a low leaching potential should be selected. When a site has groundwater near the surface and the soil is permeable, then the leaching potential of the pesticide must be considered during pesticide selection.

Applicators should read the label to find warnings that tell them that the pesticide may leach. Here is an example of language to look for in the Environmental Hazards section of the label: "This product has properties and characteristics associated with chemicals detected in groundwater. The use of this chemical in areas where soils are permeable, particularly where the water table is shallow, may result in groundwater contamination." There may also be a "Groundwater Advisory" statement on the label. Many new labels have this feature, which prove to be critical in selecting the right pesticide for the job.

Proper Pesticide Mixing and Loading Procedures

More pesticide spills occur while the pesticide is being measured and mixed than during any other part of a pesticide application. Locate the mixing/loading site away from wells, streams and lakes. Maintain a distance of at least 100 feet between the mixing and loading site and wellheads, ditches, streams or other water sources. (See Mixing/Loading)

Measure, mix, and load over an impervious surface such as a concrete pad which prevent spills from soaking into the ground. Measure the concentrate carefully to avoid spills. Using a closed transfer system to mix and load pesticides also helps reduce the risk of spills. If you are not using a pad, move the mixing and loading steps from place to place to avoid buildup of contamination from accidental splashes or spills. (See Pesticide Spills)

Be prepared for spills and have a "spill kit" readily available. Stop spills quickly by having spill control tools and materials close at hand near the mixing/loading area. Never leave a tank while it is being filled and pay constant attention during filling to prevent overfilling and spilling of the pesticide on the ground. Be disciplined and patient. Wait by the tank until filling is completed.

Applicators should read the label carefully to find warnings regarding mixing/loading pesticides. Here is a statement found in the Environmental Hazards section of many labels: "Most cases of groundwater contamination involving this pesticide have been associated with mixing/loading and disposal sites. Caution should be exercised when handling this product at such sites to prevent contamination of groundwater supplies. Use of closed systems for mixing or transferring this pesticide will reduce the probability of spills. Placement of the mixing/loading equipment on an impervious pad to contain spills will help prevent groundwater contamination."

Choose this link for more information on mixing and loading pesticides:
http://www.al.gov.bc.ca/pesticides/d_5.htm

Prevent Pesticide Backflow

Backflow occurs when a water supply loses pressure and starts flowing backwards toward the water source. The backward flow creates a siphon that draws some of the contents of the sprayer tank back toward the water source if a pipe or hose is below the water surface in the tank. If backflow occurs, the water supply pipes, pumps, and well become contaminated by pesticides from the tank. An anti-siphon device (check valve) prevents backflow and the resulting contamination from occurring. Proper anti-siphoning techniques include the use of a reduced pressure zone (anti-siphon) device or an air gap between the filler pipe and the tank.

Choose any of these links for more information on backflow prevention:
http://pmep.cce.cornell.edu/facts-slides-self/facts/gen-peapp-back-siph.html
http://www.ag.uiuc.edu/~vista/html_pubs/back/back.htm

Proper Application Procedures

Proper application of pesticides starts with calibration. Calibrating application equipment is the only way to be sure that the proper amount of pesticide is applied. Application of excess pesticide increases the risk of contaminating water by overloading the protective mechanisms of degradation and adsorption, making them ineffective. Over application is not only risky for the environment, but is a violation of label directions and the law.

Knowledge of the application site is very important for preventing water contamination. You should know where wells are located, the depth to groundwater, and where surface water is located before making an application. After identifying these features, make plans to protect them. Decide where to turn the application equipment on and off ahead of time. Don't try to make these decisions on the fly! Using buffer zones and setback areas creates safety zones by keeping applications away from sensitive areas, particularly surface waters. Pesticide applications should hit the target precisely. Applications that move off-target can contribute to water contamination.

Preventing drift is another important task of the applicator. Drifting pesticide can contaminate water and cause other problems. Setting the boom height as close as possible to the target and selecting the proper nozzle type are important decisions that help reduce the chance of pesticide drift contaminating surface waters.

Irrigation Management

Increasing the amount of water that lands on the soil surface increases the chance that pesticides will migrate to groundwater and surface water resources. Water falling on saturated soils or at a rate that exceeds the infiltration rate of soil promotes runoff that can carry pesticides with it. Precipitation or irrigation that promotes the frequent downward movement of water beyond the root zone of plants also promotes the leaching of substances, including pesticides, to groundwater. This is of particular concern in areas where frequent irrigation is necessary because of coarse-textured soils. Proper irrigation management is critical to minimize the risk of pesticides moving to groundwater.

Proper Pesticide Storage

Proper storage of pesticides is also important to prevent water contamination. Locking pesticides inside a fire resistant, spill-proof facility is an excellent way to prevent accidental pesticide spills. Proper storage is very cheap compared with the expensive consequences of accidents, spills, or fires. Be prepared for spills and have a "spill kit" readily available. Stop spills quickly by having spill control tools and materials close at hand inside or near the storage area. (See Pesticide Storage)

Proper Disposal of Pesticides and Containers

Pesticide containers that have not been triple rinsed pose a risk to water resources. Contaminated containers left outside and exposed to rain can leach pesticides into the environment. Triple rinsing pesticide containers prior to disposal removes pesticide residues. Water collected from cleaning and rinsing application equipment should be applied to the original site of the application. Be careful not to exceed label rates. Re-using this pesticide-contaminated water is an environmentally responsible way to dispose of this material. Collect rinsed containers in a dry, secure, and protected area for disposal. Dispose of the rinsed containers following label directions and local ordinances. Use pesticide container recycling programs where available. (See Pesticide Disposal)

Authored by Ronald D. Gardner