Table 3-6: Agricultural/Rural On-Farm Assessments (Back to Document)

1. Private Wells: (Point Sources)

These wells might not be drilled to the same depth as a larger community well but if improperly constructed or maintained, may provide a conduit or direct route for contaminant movement into groundwater.

Factors to Assess:

  • Position of well in relation to pollution sources.
  • Potential of soil around well to protect.
  • Depth to the aquifer.
  • Condition of casing and well cap (seal).
  • Placement of casing or grout seal.
  • Well age.
  • Well type.
  • Backflow prevention.
  • Frequency of water testing.
2. Abandoned Wells: (Point Sources)

An improperly abandoned well provides a direct route for contaminants to underground water supplies which recharge the aquifer supplying the well which is being protected. The worst scenario occurs when wastes are dumped directly into an old well. Unintentional contaminant flow into an old well should also be prevented. Current owners of a site may not even be aware of wells that were abandoned by the previous owners. Since abandoned wells can provide a direct route for contaminants to the groundwater, not knowing they exist at a site could create a high risk situation. The Local Team may wish to consult historical documents or older community members, if time and resources permit, for the location of abandoned wells.

Factors to Assess:

  • Was the well properly abandoned according to the standards of The Oregon Water Resources Department?
  • Is the abandonment temporary or permanent?
  • Where is the well location relative to stored controlled material; where agricultural chemicals are being applied; to drinking water well?
3. Pesticide Storage and Handling Areas: (Point Sources)

Pesticides here would include insecticides, herbicides, fungicides, or any other chemical or biological agent used to control destructive organisms. Storage and handling areas involve placing a large concentration of farm chemicals in a small area. Furthermore, the chemicals may be packaged in concentrated form to be diluted before application. If precautions are not taken to prevent leakage or spillage onto the soil, a much higher risk of groundwater contamination can occur here than when diluted chemicals are correctly applied over a large area of cropland. Even small spills, repeated often in this one area, can add up to a serious problem.

Factors to Assess:

  • Amount stored.
  • Types stored (the leaching potential of each).
  • Liquid or dry formulations.
  • Handling procedures.
  • Spill or leak control.
  • Types of containers used and disposal of containers (See: "Pesticide Container Management Program" in the Resource List).
  • Security of storage area.
  • Location and slope from any wells.
  • Mixing pad or containment structure/equipment.
  • Water source for mixing and backflow prevention.
  • Supervision/qualifications/training of personnel.
  • Material transfer system.
  • Sprayer/tank cleaning and disposal of rinsate.
  • Appropriate emergency plan.
4. Fertilizer Storage and Handling Areas: (Point Sources)

Fertilizers should include any type of soil amendment which is being stored or handled in the WHPA. Synthetic fertilizer (bulk or containerized) and organic fertilizer (manure) should be included in the assessment. The same reasoning applies to these areas as to pesticide storage and handling areas. A concentrated amount of a substance in a small area must be safeguarded against leakage and spillage.

Factors to Assess:

  • Amount stored.
  • Type of storage.
  • Containers used for storage or cover over storage.
  • Security of storage area.
  • Location and slope from any wells.
  • Spill containment pad or equipment.
  • Water source for mixing and backflow prevention.
  • Supervision/qualifications of personnel.
  • Material transfer system.
  • Sprayer/tank cleaning and disposal of rinsate.
  • Appropriate emergency plan.
5. Livestock Waste Storage and Treatment: (Point Sources)

Even small amounts of solid livestock waste could pose a threat to groundwater if stored. Any water seeping through the solid waste could carry harmful leachate to the wellhead.

Factors to Assess:

  • Duration of storage (short- or long-term).
  • Cover over storage area.
  • Contained or stacked in field.
  • Containment structure (liquid-tight above or below ground or earthen waste pond).
  • Location and slope to nearest well.
  • Composting of manure.
6. Petroleum Product Storage and Handling: (Point Sources)

This category includes the storage of petroleum products other than fuel such as lubricating oils, hydraulic oils and coolants commonly required for farm equipment maintenance and operation. Whether new or used (See also: "Hazardous Waste Management") these products should be prevented from leaking or spilling onto the soil where they could pose a threat to groundwater.

Factors to Assess:

Fuel Tanks:

  • Above or below ground tank.
  • Used or abandoned tank.
  • Location of tank in relation to nearest well.
  • Slope relation to well and position in relation to the water table depth.
  • Soil permeability around or under tank.
  • Type and age of tank, corrosion protection.
  • Overfill protection.
  • Piping and hoses.
  • Professional or improper/unknown installation.
  • Tank enclosure or secondary containment if above ground tank.
  • Tank testing or leak monitoring.

Lubricants/Hydraulic Fluids/Coolants:

  • If large quantities are stored in tanks the same factors as for fuel tanks listed above may apply.
  • Dry storage to prevent rainwater from carrying contaminants to soil.
  • Condition of containers and proper labels.
  • Spillage and leakage prevention.
  • Recycling or proper disposal of used oils/fluids and their containers.
7. Hazardous Waste Management: (Point Sources)

Contaminated fuel, used oil being saved for recycling, used coolant, used hydraulic fluid, old vehicle/tractor batteries and other common farm waste items should be addressed here if they are stored in the WHPA. Any of these items leaking or spilling onto the soil could pose a threat to the groundwater.

Factors to Assess:

  • Ash disposal from incineration.
  • Disposal of leftover/ineffective adhesives, cleaning solvents, lead-based paint, stain and paint strippers/thinners or other farm chemicals.
  • Disposal of containers (See Resource List for information on the container disposal program).
  • Vehicle maintenance products such as oil,antifreeze, brake fluid and hydraulic fluid (new and used forms).
  • Used vehicle/equipment batteries.
8. Household Wastewater Management: (Point Sources)

This is a category also addressed in residential practices. The location and condition of wastewater drainfields would need to be addressed here if they were located in the WHPA. An overloaded or poorly maintained system could introduce wastewater contaminants to the groundwater.

Factors to Assess:

  • Quantity generated.
  • Quality of wastewater.
  • Collection of wastewater.
  • Pretreatment system.
  • Disposal system.
  • Pump-out of septic tanks or other systems.
9. Farm or Farm Household Waste Disposal/Fill Areas: (Point Sources)

Farms traditionally had an area set aside for the convenient disposal of wastes generated on the farm. If such an area exists in a WHPA it should be very carefully managed. Animal burial areas may also be a concern that could be addressed here if within the WHPA. Disposal in unlined earthen pits of any of these wastes may have a high potential of contaminating groundwater.

Factors to Assess:

  • Soil type in disposal area (permeability).
  • Lining of disposal pit.
  • Improper disposal of hazardous wastes.
  • Disposal of liquid wastes.
  • Animal burial (restricted in many states).
  • Unmonitored public use of disposal area.
10. Milking Center Wastewater Handling Facilities: (Point Sources)

As with household wastewater, the discharge points or area would need to be assessed if within the wellhead protection area. Milking center wastewater could be discharged to underground or surface treatment areas directly or stored for slow release. If stored, the storage tank or lagoon condition would need to be checked for possible threat to groundwater in the wellhead protection area. Unlined earthen storage pits may permit leakage of untreated wastewater to the groundwater.

Factors to Assess:

  • Storage of wastewater (if combined with CAFO wastes see factors in that category).
  • Milking cleanup practices.
  • Lining of storage/settling tank.
  • Storage duration.
  • Distance of discharge from well.
  • Discharge method.
11. Confined Animal Feeding Operations (CAFO): (Point Sources)

If an area is used to confine livestock and the soil is exposed, excess nutrients from the manure could pose a threat to groundwater. Runoff from this area is a high strength waste and if it enters a permeable area can carry a significant pollutant load to surface water and/or groundwater.

Factors to Assess:

  • Distance from well.
  • Soil permeability.
  • Livestock water source.
  • Surface water diversion.
  • Lot runoff control.
  • Yard cleaning and scraping practices.
  • Type of livestock.
  • Concentration of livestock (square feet/animal or no. animals/acre).
12. Livestock Grazing and Pastures: (Non-Point Sources)

As above, animal wastes may be of concern here or the application of chemicals to pasture lands for weed control. Areas where the livestock congregate for feed, water, or shade become denuded of vegetation. The vegetation which might trap and use the excess manure nutrients, and thus prevent them from leaching to the groundwater, is absent.

Factors to Assess:

  • Placement of livestock watering facilities.
  • Herd management areas and paddock layout.
  • Chemical application to pasture.
  • Density of livestock in pasture.
13. Crop Production - Non-Irrigated & Irrigated: (Non-Point Sources)

This category is primarily concerned with the improper application of farm chemicals to crops in the field. If care is not taken to carefully manage application of chemicals, the excess materials may leach to the groundwater. The "Oregon Water Quality Decision Aid" may be useful here in the assessment and later on in the management plan. Other Extension documents are available from Oregon State University which might aid in the assessment process with regards to pesticide application and soil vulnerability, namely: EM8559, EM8560 and EM8561 (SEE: Resource List for how to acquire these and other helpful documents).

Irrigation of crops has the potential to increase the rate of travel of materials to the groundwater. Irrigation water is sometimes intentionally used to conveniently distribute chemicals or fertilizer (chemigation, fertigation) precisely when the plants need them. This can have either a positive or negative effect on groundwater depending on management.

Factors to Assess:

  • Weed control (including control of "volunteer" crop plants from the previous growing season which may sustain crop pests and thus create a need for greater pesticide use).
  • Realistic yield goals.
  • Site-specific management of chemical application.
  • Soil type and regular soil testing; assessment of mineralization.
  • Nutrient application timing and rates.
  • Use of integrated pest management for efficiency.
  • Nitrification inhibitors/slow release nitrogen.
  • Integration of manure and fertilizer use.
  • Use of tramlines (designated paths through fields for tractor) for precision application of chemicals.
  • Sprayer maintenance and calibration.
  • Pesticide selection and application method, timing, and rates.
  • Rotating chemicals with different modes of action.
  • Buffer zones, especially around wells.
  • Riparian/wetland protection (vegetation which can utilize/filter excess nutrients or chemicals from cropland).
  • Subsurface drainage.
  • Crop rotation and post harvest covercrop.
  • Irrigation management and monitoring.
  • Amount of water applied matched to soil water holding capacity and crop requirements.
  • Chemigation/fertigation systems: backflow prevention valves, low pressure drain discharge away from well, chemical injection line check valve, automatic synchronization of chemical injection and water pump.


Each source is labeled as either a potential "point source" of contamination, as might occur near farm buildings and households, or as a potential "non-point" source, as might occur in the fields. Some of the BMP guides will also make this distinction. One is not necessarily more or less of a threat than the other. Point sources are sometimes easier to control because they may be more readily located and identified.