University of Missouri Extension

WQ652, New October 1995

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 EQ676, 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

  • Use a pencil. You may want to make changes.
  • For each category listed on the left that is appropriate to your farmstead, read across to the right and circle the statement that best describes conditions on your farmstead. (Skip and leave blank any categories that don't apply to your farmstead.)
  • Then look above the description you circled to find your "rank number" (4, 3, 2 or 1) and enter that number in the blank under "your rank."
  • Directions on overall scoring appear at the end of the worksheet.
  • Allow about 15 minutes to 30 minutes to complete the worksheet and figure out your risk ranking for well-management practices.
  Low risk, rank 4 Low to moderate risk, rank 3 Moderate to high risk, rank 2 High risk, rank 1 Your rank
Pesticide storage
Amount stored No pesticides stored at any time. Less than 1 gallon, or more than 10 pounds of each pesticide. More than 1 gallon, or more than 10 pounds of each pesticide. More than 55 gallons, or more than 550 pounds of each pesticide.  
Location of pesticide storage area in relation to well 300 feet or more downslope from well. 50 to 300 feet downslope from well. 150 to 150 feet downslope from well.1 Within 50 feet or up-slope from well.1  
Leachability (See Pesticide chart.)

Liquid or dry formulation
No pesticides stored.

No liquids. All dry.
Pesticides classified as having low leaching potential.

Some liquids. Mostly dry.
Pesticides classified as having medium leaching potential.
Mostly liquids. Some dry.
Pesticides classified as having high leaching potential.

All liquids.
Spill or leak control in storage area Impermeable surface (such as concrete), does not allow spills to soak into soil. Curb installed on floor to contain leaks and spills. Impermeable surface with curb installed has some cracks, allowing spills to get to soils. OR impermeable surface without cracks, has no curb installed. Permeable surface (wooden floor), has some cracks. Impermeable surface, has no curb. Spills could contaminate wood or soil. Permeable surface (gravel or dirt floor). Spills could contaminate floor.  
Containers Original containers clearly labled. No holes, tears or weak seams. Original containers old. Labels partially missing or hard to read. Containers old but patched. Metal containers show signs of rusting. Containers have holes or tears that allow chemicals to leak. No labels.  
Security Fenced or locked area separate from all other activities. Fenced area separate from most other activities. Open to activities that could damage containers or spill chemicals. Open access to theft, vandalism and children.  
Mixing and loading practices
Location of well in relation to mixing/loading area with no curbed and impermeable containment area 150 feet or more from well. 100 to 150 feet downslope from well1 50 to 100 feet downslope from well,1or 100 to 500 feet upslope. Within 50 feet downslope, or within 100 feet upslope from well.1  
Mixing and loading pad (Spill containment) Concrete pad with curb keeps spills contained. Sump allows collection and transfer to storage. Concrete pad with curb keeps spills contained. No sump. Concrete pad with some cracks keeps some spills contained. No curb or sump. No mixing/loading pad. Permeable soil (sand). Spills soak into ground.  
Backflow prevention on water supply Anti-backflow device installed or 6-inch air gap maintained above sprayer tank. Anti-backflow device installed. Hose in tank above waterline. No anti-backflow device. Hose in tank above waterline. No anti-backflow device. Hose in tank below water line.2  
Water source Separate water tank Hydrant away from well. Hydrant near well. Obtained directly from well.  
Filling supervision Constant supervision Frequent. Seldom. Never.  
Handling system Closed system for all liquid and dry product transfers. Closed system for most liquids. Some liquid and dry product hand poured. Sprayer fill port easy to reach. All liquids and dry product hand poured. Sprayer fill port easy to reach. All liquids and dry product hand poured. Sprayer fill port hard to reach.  
Sprayer cleaning and rinsate (rinse water) disposal Sprayer washed out in field. Sprayer washed out on pad at farmstead. Rinsate used in next load and applied to labeled crop. Sprayer washed out at farmstead. Rinsate sprayed less than 100 feet from well. Sprayer washed out at farmstead. Rinsate dumped at farmstead or in field.2  
Container disposal
Disposal location Triple-rinsed containers returned to dealers or taken to licensed landfill or municipal incinerator. Bags returned to supplier, or hazardous waste collection service used. Unrinsed containers and empty bags taken to licensed landfill, municipal incinerator or dump. Disposal of unrinsed containers or empty bags on farm. Disposal of triple-rinsed containers on farm. Disposal of partially filled plastic or paper containers on farm. Bags buried in field or burned on farm.  
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.

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

The pesticides listed on this chart are identified by brand name, common name and rating for movement by leaching (low, medium or high). Identify the pesticides stored on your farmstead from the listing below. Note the "leachability factor" for each pesticide you store. Then give yourself an overall "leachability ranking" (low, medium or high), based on which ranking best represents the pesticides you store. Then use this ranking to complete the "Leachability" section on the assessment worksheet.
Brand name Common name Rating for movement by leaching
Alanap naptalam  
Ally metsulfuron-methyl  
Amiben chloramben  
AmitrolT amitrole Med
Antor diethatyl-ethyl Low
Arsenal imazapyracid High
Arsenal imazapyramine High
Assert imazethabenz High
Assure quizalofop ethyl Low1
Atrazine atrazine High
Avenge difenzoquat Low
Balan benefin Low
Banvel dicamba High
Basagran bentazon High
Betamix phenmedipham and desmedipham Low
Betanex desmedipham Low
Bicep metolachlor and atrazine Med
Bladex cyanazine Med
Blazer acifluorfen Med
Bronate bromoxynil and MCPA ester Low
Bronco glyphosate and alachlor Low
Buckle triallate and trifluralin Low
Buctril bromoxynil Low
Buctril-Atrazine bromoxynil and atrazine Low
Butyrac 200 2,4-DB amine Med1
Butyrac 2,4-DB ester Low1
Cannon alachlor and trifluralin Med
Carbyne barban  
Casoron dichlobenil High
Classic chlorimuron  
Cobra lactofen  
Command clomazone Med
Commence trifluralin and clomazone Low
Crossbow triclopyr and 2,4-D ester Med
Curtail clopyralid and 2,4-D amine High
CurtailM clopyralid and MCPA ester High
Dacthal DCPA Low
Dowpon dalapon High
Dual metolachlor Med
Eptam EPTC Med
Eradicane EPTC Med
Eradicane Extra EPTC Med
Evik ametryn Med
ExtrazineII atrazine and cyanazine High
Far-Go triallate Low
Fusilade 2000 fluazifop Low
Galaxie bentazon and aciflourfen High
GenatePlus butylate Med
Genep EPTC Med
Glean chlorsulfuron  
Goal oxyfluorfen Low1
Gramoxone Extra paraquat Low
Harmony DPX-M6316 and Extra DPX-L5300  
Herbicide 273 endothall Low
Hoelon diclofop Low
Kerb pronamide Low
Krenite fosamine Low
Laddock atrazine and bentazon High
Lariat alachlor and atrazine Med
Lasso EC alachlor Med
Lasso Micro Tech alachlor  
LassoII alachlor Med
Lasso- Atrazine alachlor and atrazine Med
Lexone metribuzin High
Lorox linuron Med
LoroxPlus linuron and chlorimuron Med
Marksman dicamba and atrazine High
MCPA Amine MCPA amine  
MCPA Ester MCPA ester Low
Nortron ethofumesate High
Option fenoxaprop Low
Pinnacle DPX-M6316  
Poast sethoxydim  
Pramitol prometon High
Preview metribuzin and chlorimuron High
Princep simazine High
Prowl pendimethalin Low
Prozine pendimethalin and atrazine Low
Pursuit imazethapyr  
Pursuit Plus imazethapyr and pendimethalin -
Pyramin pyrazon High
Ramrod propachlor Low
Ramrod- Atrazine propachlor and atrazine Low
atrazine High
Ranger glyphosate Low
Reflex fomesafen High
Rescue naptalam and 2,4-DB Med1
Rhino butylate and
Ro-Neet cycloate Med
Roundup glyphosate Low
Salute metribuzin and trifluralin High
Scepter imazaquin  
Sencor metribuzin High
Sinbar terbacil High
Sonalan ethalfluralin Low
Spike tebuthiuron High
Stampede CM propanil and MCPA ester Low
Stinger clopyralid High
Storm bentazon and acifluorfen High
Surflan oryzalin Low
Sutan+ butylate Med
Sutazine+ butylate and atrazine Med
2,4-D amine 2,4-D amine Med
2,4-D ester 2,4-D ester Low1
Tandem tridiphane Low
Thistrol MCPB  
Tillam pebulate Med
Tordon picloram High
Treflan trifluralin Low
Turbo metolachlor and metribuzin Med
Velpar hexazinone High
Vernam vernolate Low
Weedar MCPA amine  
Weedmaster dicamba and
2,4-D amine
Weedone- 2,4-DP dichlorprop ester -
Whip fenoxaprop Low
Ambush permithrin Low
Aqua8-Parathion parathion Low
AsanaXL esfenvalerate Low
Bolstar sulprofos Low
Broot trimethacarb Low2
Carzol formetanate Low
Counter terbufos Low
Cygon dimethoate Med
Cythion malathion Low
Diazinon diazinon Med1
Dimilin diflubenzuron Low
DiSyston disulfoton Low
Dyfonate fonofos Med
DyfonateII fonofos Med
Dylox trichlorfon High
Endocide endosulfon Low
Endocide Plus endosulfon and parathion High
Force tefluthrin  
Furadan carbofuran High
Guthion azinphos-methyl Low
Imidan phosmet Low
Knox-Out diazinon Med1
Lannate methomyl High
Larvadex cyromazine High1
Larvin thiodicarb Low
Lindane lindane Med
Lorsban chlorpyrifos Low
Malathion malathion Low
Malathion/ methoxychlor malathion and methoxychlor Low
Mavrik fluvalinate Low
Metasystox-R demeton-s-methyl High2
Methoxychlor methoxychlor  
Mitac amitraz Low2
Mocap ethoprop High
Monitor methamidophos High
Nudrin methomyl High
Orthene acephate Low
Parathion parathion Low1
Penncap-M methyl parathion Low
Phosdrin mevinphos Med
Phoskil parathion Low1
Pounce permethrin Low
Pydrin fenvalerate Low
Rampart phorate Low
Scout-Xtra tralomethrin  
Sevin carbaryl Low
Somanil methidathion Med
Supracide methidathion Med
Swat phosphamidon  
Temik aldicarb High
Thimet phorate Low
Thiodan endosulfan Low
Trigard cyromazine High1
Vydate oxamyl Low
Agsco TN-IV tin  
Agsco MNF maneb and
Bayleton triadimefon Med
Benlate benomyl High
Blitex maneb and triphenyltin Low2
Botran dicloran Low2
Bravo chlorothalonil Low
Captan captan Low
Carbamate ferbam Med
Champion copper-fixed  
Crotothane dinocap Low2
Cyprex dodineacetate Low2
Daconil chlorothalonil Low
Dithane mancozeb Low
Duter tin  
Dyrene anilazine Low
Karathane dinocap Low2
Kelthane dicofol Low2
Kocide copper hydroxide  
Magnetic sulfur  
Maneb maneb Low2
Maneb and maneb and Low2
Zinc zinc  
Manzate mancozeb Low
Merteck thiabendazole  
Orbit propiconazole Med2
Penncozeb mancozeb Low
Polyram metiram Low2
Protex maneb triphenyltin Low2
Ridomil metalaxyl High
Ronilan vinclozalin Low2
Rovral iprodione Low1
Rubigan fenarimol High
SuperSix sulfur  
SuperTin tin  
TeloneII dichloropropene Med
Terrachlor PCNB Low1
Tersan benomyl High
ThatF sulfur  
Thiolux sulfur  
Tilt propiconazole Med2
TopCop basiccoppersulfate  
Topsin thiophanatemethyl Low2
Triphenyl Tin triphenyltin  
Hydroxide hydroxide  
TripleTin triphenyltin hydroxide  
Vitavax carboxin Low
Vorlex dichloropropene and
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

________ divided by ________ equals ________
(total of rankings)   (number of categories ranked)   (risk ranking1)
1Carry your answer out to one decimal place.
If your risk ranking is Your risk is
3.6 to 4 low
2.6 to 3.5 low to moderate
1.6 to 2.5 moderate to high
1 to 1.5 high

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:

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 EQ675), Improving Drinking-Water Well Conditions, and consider how you might modify your farmstead practices to better protect your drinking water.


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 EQ675).

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 Assessing the Risk of Groundwater Contamination From Pesticide Storage and Handling | University of Missouri Extension

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