Assessing the Risk of Groundwater Contamination From Fertilizer Storage and Handling
Farm•A•Syst: Farmstead Assessment System Worksheet #3
Fertilizers play a vital role in agriculture. Over the years, they have increased farm production dramatically. Commercial fertilizer is, however, a major source of nitrate. Nitrate-nitrogen levels exceeding the public health standard of 10 milligrams per liter (mg per liter; equivalent to parts per million for water measure) have been found in many drinking-water wells. The other major components of commercial fertilizer, phosphorus and potassium generally are not a groundwater-contamination concern.
Nitrate levels in drinking water above federal and state drinking-water standards of 10 milligrams per liter nitrate-nitrogen can pose a risk to some infants. Infants younger than 6 months of age are susceptible to health problems from high nitrate-nitrogen levels, including the condition known as methemo-globinemia (blue baby syndrome). Nitrate also can affect adults, but the evidence is much less certain.
Young livestock are particularly susceptible to health problems from high nitrate-nitrogen levels.
Although livestock may be able to tolerate several times the 10 milligrams per liter nitrate-nitrogen level, levels of 20 to 40 milligrams per liter may prove harmful, especially in combination with high levels (1,000 ppm) of nitrate-nitrogen from feed sources.
Handling fertilizers can affect groundwater by allowing materials containing nitrogen to seep through the ground after a leak or spill. Other potential farmstead sources of nitrate are septic systems, livestock yards, livestock-waste storage facilities and silage storage.
Your drinking water is least likely to be contaminated if you follow appropriate management procedures or dispose of wastes at an 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. The goal of Farm•A•Syst is to help you protect the groundwater that supplies your drinking water.
How will this worksheet help me protect my drinking water?
It will take you step by step through your fertilizer handling, storage 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 fertilizer handling, storage 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.
How do I complete the worksheet?
Follow the direction at the top of the following chart. It should take you about 15 to 30 minutes to complete this worksheet and figure out your ranking.
Fertilizer 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
|Location of storage area in relation to well
Type of storage
|300 feet or more downslop from well
None stored at any time.
Covered on impermeable surface (such as cocrete or asphalt). Spills are collected.
|150 to 300 feet downslope from well1
Less than 1 ton.
Covered on clay soil. Spills are collected.
|50 to 150 feet downslope from well1
Between 1 and 3 tons.
Partial cover on loamy soils. Spills not collected.
|Within 50 feet or upslope from well1
More than 3 tons.1
No cover on sandy soils. Spills not collected.
Type of storage
|None stored at any time
Concrete or other impermeable secondary containment does not allow spill to contaminate soil.
|Less than 55 gallons.
Clay-lined secondary containment. Most of spill can be recovered.
|Between 55 and 500 gallons.1
Somewhat permeable soils (loam). No secondary containment. Most of spill cannot be recovered.
|More than 500 gallons.1
Permeable soil (sand). No secondary containment. Spills contaminate soil.
||Original containers clearly labeled. No holes, tears or weak seams. Lids tight.
||Original containers old. Labels partially missing or hard to read.
||Containers old but patched. Metal containers showing signs of rusting.
||Containers have holes or tears that allow fertilizers to leak. No labels.
||Fenced or locked area separate from all other activities, or locks on valves.
||Fenced area separate from most other activities.
||Open to activities that could damage containers or spill fertilizer.
||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 or more feet downslope from well.
||100 to 150 feet downslope.
||50 to 100 feet down-slope,1 or 100 to 500 feet upslope.
||Within 50 feet downslope,1 or 100 feet upslope.
|Additional mixing and loading practices for liquid fertilizer
|Mixing and loading pad (spill containment)
||Concrete mixing/loading pad with curb keeps spills contained. Sump allows collection and transfer to storage.
||Concrete pad with curb keeps spills contained. No sump.1
||Concrete pad with some cracks keeps some spills contained. No curb or sump.
||No mixing/loading pad. Permeable soil (sand). Spills soak into ground.
||Separate water tank.
||Hydrant away from well.
||Hydrant near well.
||Directly obtained from well.
|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-anti-backflow device. Hose in tank below water line.
||Seldom or never.
||Closed system for all liquid-product transfers.
||Closed system system for most liquids. Some liquids hand poured. Sprayer fill port easy to reach.
||All liquids hand poured. Sprayer fill port easy to reach.
||All liquids hand poured. Sprayer fill port hard to reach.
|Sprayer cleaning and rinsate (rinse water) disposal
||Sprayer cleaning and rinsate (rinse water) disposal
||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 nearby field.
|Use this total to calculate risk ranking in Equation 1.
1If facility stores more than 5,000 pounds of dry material or more than 500 gallons of liquid, a facility permit must be obtained from the Missouri Department of Natural Resources through an approved engineer.>
What do I do with these rankings?
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:
|(total of rankings)
||(number of categories ranked)
1Carry your answer out to one decimal place.
|If your risk ranking is
||Your risk is
|3.6 to 4
|2.6 to 3.5
||low to moderate
|1.6 to 2.5
||moderate to high
|1 to 1.5
This ranking gives you an idea of how your fertilizer-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 fertilizer 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.
Look over your rankings for individual activities:
- Low-risk practices (4s): ideal; should be your goal despite cost and effort
- Low- to moderate-risk practices (3s): provide reasonable groundwater protection
- Moderate- to high-risk practices (2s): inadequate protection in many circumstances
- High-risk practices (1s): inadequate; pose a high risk of polluting groundwater
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).
Read Fact Sheet #3 (MU publication WQ677), Improving Fertilizer Storage and Handling, and consider how you might modify your farmstead practices to better protect your drinking water.
Fertilizer storage and handling glossary
These terms may help you make more accurate assessments when completing Worksheet #3. They also may help clarify some of the terms used in Fact Sheet #3 (MU publication WQ677).
- Air gap
An air space (open space) between the hose and 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.
The unwanted flow of liquids in a piping system.
- Backflow-prevention device
See anti-backflow device).
Backflow caused by formation of a vacuum in a water-supply pipe.
- Closed handling system
A system that transfers pesticides or fertilizers directly from storage container to applicator equipment (through a hose, for example) so humans and the environment are never inadvertently exposed to the chemicals.
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.
- Milligrams per liter (mg per liter)
The weight of a substance measured in milligrams contained in 1 liter. It is equivalent to 1 part per million in water measure.
- Parts per million (ppm)
A measurement of concentration of one unit of material dispersed in one million units of another.
Rinse water from pesticide or fertilizer tank cleaning.
- Secondary containment
Impermeable floor and walls around a chemical storage area that minimize the amount of chemical seeping into the ground from a spill or leak.
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.
WQ653, new October 1995