• spillage of fertilizers and pesticides during handling
• runoff from the loading and washing of pesticide sprayers or other application equipment
• using chemicals uphill from or within a few hundred feet of a well

Agricultural land that lacks sufficient drainage is considered by many farmers to be lost income land. So they may install drain tiles or drainage wells to make the land more productive. The drainage well then serves as a direct conduit to ground water for agricultural wastes which are washed down with the runoff.

Storage of agricultural chemicals near conduits to ground water, such as open and abandoned wells, sink holes, or surface depressions where ponded water is likely to accumulate. Contamination may also occur when chemicals are stored in uncovered areas, unprotected from wind and rain, or are stored in locations where the ground water flows from the direction of the chemical storage to the well.

Mixing and distributing pesticides and fertilizers with irrigation water can cause ground water contamination if more chemicals are applied than crops can use. Irrigation also poses a problem if chemicals back-siphon from the holding tank directly into the aquifer through an irrigation well.

Fields with overapplied or misapplied fertilizers, herbicides, insecticides and fungicides could introduce these contaminants into the ground water:

• Many organic compounds
• Excess nitrogen
• Cadmium
• Chloride
• Mercury
• Selenium

Feedlots are potential contamination sources. Animal waste is often collected in impoundments from which the wastes may infiltrate the ground water. Runoff could also enter an aquifer through a poorly sealed well casing. Livestock waste is a source of:

• Nitrate
• Coliform Bacteria
• Total Dissolved Solids
• Sulfates

Within the garage or farm equipment shed, chemicals that are improperly stored or disposed of that could potentially contaminate ground water include:

• Paint containing lead and barium
• Gasoline and oils containing volatile organic compounds
• Barium from diesel fuel combustion
• Rinsate containing residues of pesticides or fertilizers

Many sources of ground water contamination can originate in the house or other farm residences such as trailers or dormitories. Leaks, spills, overloading, or poor maintenance of septic systems can result in the following contaminants entering ground water:

• Coliform Bacteria
• Nitrate
• Total Dissolved Solids
• Chloride
• Sodium
• Sulfates
• Detergents
• Chromium

Both aboveground and underground storage tanks (USTs) are at risk of leaking and releasing gasoline, which contains benzene.

Abandoned wells that have not been plugged or dismantled provide a potential pathway (direct route) for water to flow directly from the surface to the aquifer, carrying whatever contaminants are on the surface into the ground water.

Open wells can become contaminated by the working fluids, such as grease and oils from the pump or from contaminants from the surface if the well cap is not tight or if the casing lining the well is cracked or corroded. In addition, many older farm wells were merely shallow holes dug into the ground. These wells can easily be contaminated and are also a safety hazard to children and animals.

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