Assessing the Risk of Groundwater Contamination from

Animal Lot Management

Worksheet 8

Outside animal lots, both surfaced and unsurfaced, are areas where animal wastes concentrate. They can be a source of contamination of groundwater and surface water. This is especially true if there is no system to divert clean water flow from the animal lot or collect contaminated runoff for diversion to an area where its effect on surface water or groundwater is minimal.

The potential for animal lots to affect groundwater is greatest if the lot is unsurfaced and located over coarse-textured permeable soils, if the water table is at or near the surface, if bedrock is within a few feet of the surface, or when contaminated runoff is discharged to permeable soils and bedrock.

Nitrate-nitrogen levels in drinking water greater than federal and state drinking water standards of 10 mg/L* can pose health problems, including the condition known as methemoglobinemia (blue baby syndrome), for infants under 6 months of age. Young animals are also susceptible to health problems from high nitrate-nitrogen levels. Levels of 20-40 mg/L in the water supply may prove harmful to young animals, especially in combination with high levels (1,000 ppm) of nitrate-nitrogen from feed sources.

Microorganisms in animal waste can contaminate groundwater if waste seeps into nearby wells, increasing the potential of such infectious diseases as dysentery, typhoid and hepatitis. Organic materials, which may lend an undesirable taste and odor to drinking water, are not known to be dangerous to health, but their presence does suggest that other contaminants are flowing directly into groundwater.

The goal of Home·A·Syst is to help you protect the groundwater that supplies your drinking water.

*means milligrams per liter, equivalent to parts per million for water measure

• It will take you step by step through your animal lot management 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 animal lot management 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.

These terms may help you make more accurate assessments when completing worksheet 8. They may also help clarify some of the terms used in fact sheet 8.

Filter strip: A gently sloping grass plot used to filter runoff from the animal lot. Influent waste is distributed uniformly across the high end of the strip and allowed to flow down the slope. Nutrients and suspended material remaining in the runoff water are filtered through the grass, absorbed by the soil, and ultimately taken up by the plants. Filter strips must be designed and sized to match the characteristics of the animal lot and topography.

Holding pond: A storage area, usually earthen, where lot runoff, lagoon effluent, and other dilute wastes are stored before final disposal. It is not designed for treatment.

Infiltration: The downward entry of water into the soil surface.

Percolation: The downward movement of water through the soil.

Runoff control system: A combination of management practices that can be used together to prevent water pollution from animal lot runoff. Practices may include diversion of runoff from the lot, roof runoff systems, lot shaping, settling basins, and filter strips or buffer areas.

Settling basin: Allows separation of liquid and solid wastes by settling out solid wastes for field application or disposal.

Soil drainage class: The conditions of frequency and duration of periods of saturation or partial saturation that existed during the development of the soils, as opposed to human-altered drainage. Different classes are described by such terms as "excessively drained," "well-drained," and "poorly drained."

Soil permeability: The quality that enables the soil to transmit water or air. Slowly permeable soils have fine-textured materials, like clays, that permit only slow water movement. Moderately or highly permeable soils have coarse-textured materials, like sands, that permit rapid water movement.

Soil texture: The relative proportions of the various soil separates (clay, sand, silt) in a soil. Described by such terms as "sandy loam" and "silty clay."

Step 1: In the table below summarize your risk scores by checking the appropriate box for each risk category you answered on this worksheet.

Step 2: Look over your rankings for individual activities:

• High risk practices (1's) pose a high risk of polluting groundwater.
  
  
• Moderate-to-high risk practices (2's) are inadequate protection in many circumstances.
  
  
• Low-to-moderate risk practices (3's) provide reasonable groundwater protection.
  
  
• Low risk practices (4's) are ideal; should be your goal despite cost and effort.

Any practices in shaded areas should be carefully reviewed. Some concerns you can take care of right away; others could be major or costly projects, requiring planning and prioritizing before you take action. The long-term goal of the Home·A·Syst program is to improve homestead practices and structures, so that they are classed as low risk. Activities classed as low risk generally reflect best management practices.

Transfer any activities that you ranked in the shaded areas in step 1 to the "High-Risk Activities" table on pages 2-3 of worksheet 12.

Step 3: Read fact sheet 8, Improving Animal Lot Management, if you haven't already. Consider how you might modify your homestead practices to better protect your drinking water.

The Homestead Assessment System is a cooperative project of Washington State University Cooperative Extension, Washington Department of Ecology, and the U.S. Environmental Protection Agency Region X.

Home·A·Syst team members: Christopher F. Feise and Edward B. Adams, WSU Cooperative Extension Water Quality Coordinators; James D. LaSpina, Homestead Assessment System Project Associate.

Animal Lot Management Technical Reviewers: Ronald E. Hermanson, P. E., Cooperative Extension Water Quality Project Leader and Agricultural Engineer; Andy Werkhoven, Dairy Farmer; Anne Schwartz, Washington Tilth; John Gillies, USDA-Soil Conservation Service; John W. Bernard, Area Extension Agent (Dairy); Philip A. KauzLoric, Nonpoint Source Specialist, Washington Department of Ecology.

Adapted for Washington from material developed by the Wisconsin, Minnesota, and Kansas Cooperative Extension and Farm·A·Syst Programs. Washington Home·A·Syst development was supported by the National Farmstead Assessment Program.

Information derived from Home·A·Syst worksheets is intended only to provide general information and recommendations to rural dwellers regarding their own homestead practices. It is not the intent of this educational program to keep records of individual results.