Assessing the Risk of Groundwater Contamination from

Animal Manure Storage

Worksheet 7

Farmers store animal manure so they can spread manure when crops need the nutrients. They save money because they don't need to purchase as much fertilizer. Accumulating manure in a concentrated area, however, can be risky to the environment and to human and animal health. Poorly designed or mismanaged manure storage systems can allow contamination of groundwater or surface water sources by the nutrients and disease-causing organisms contained in animal wastes.

Facilities which store manure in liquid form on the homestead may leak or burst, releasing large volumes of pollutants. Manure in earthen pits usually forms a semi-impervious seal of organic matter that does limit leaching potential, but seasonal filling and emptying can cause the seal to break down. Short-term solid manure storage and abandoned storage areas can also be sources of nitrate contamination of groundwater.

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

Microorganisms in animal manure can contaminate groundwater, causing such infectious diseases as dysentery, typhoid, and hepatitis. Organic materials that lend an undesirable taste and odor to drinking water are not known to be dangerous to health, but their presence suggests that other contaminants can be flowing 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 manure storage 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 manure storage 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 7. They may also help clarify some of the terms used in fact sheet 7.

Composting Facility: A facility for the biological stabilization of manure organic material.

Concrete stave storage: A type of liquid-tight animal manure storage structure. Located on a concrete pad, it consists of concrete panels bound together with cables or bolts and sealed between panels.

Earthen basin or pond: Clay-lined manure storage facility constructed according to specific engineering standards. Not simply an excavation.

Engineering standards: Design and construction standards available at Soil Conservation Service (SCS) or Cooperative Extension offices. These standards may come from SCS technical guides, state regulations, or land grant university engineering handbooks.

Filter strip: A gently sloping grass plot used to filter runoff from the livestock lot and some types of solid manure storage systems. 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 plants. Filter strips must be designed and sized to match the characteristics of the animal lot or storage system.

Glass-lined steel storage: A type of liquid-tight, above-ground animal waste storage structure. Located on a concrete pad, it consists of steel panels bolted together and coated inside and outside with glass to provide corrosion protection.

Manure storage pond: An impoundment made by excavation or earthfill for temporary storage of animal or other agricultural waste.

Manure treatment lagoon: An impoundment made by excavation or earthfill for biological treatment of animal or other agricultural waste.

Nutrient management plan: A plan to manage the amount, form, placement, and timing of applications of plant nutrients.

Poured concrete storage (manure tank): A type of liquid-tight animal manure storage structure. Located on a concrete pad, it consists of poured concrete reinforced with steel, and may be aboveground or below ground.

Water table depth: Depth to the upper surface of groundwater. This depth is sometimes indicated in the county soil survey, but it varies from county to county. This information may be available from your well construction report or from hydrogeological reports and groundwater flow maps of your area. Your county Cooperative Extension agent, SCS specialist, or local well driller may also be able to help you gather this information.

There are two types of water table: (1) the water table typically noted in a well log as an indication of usable water supply; and (2) the seasonal high water table. The seasonal high water table is more important in regard to construction of animal manure storage facilities because it may present facility construction problems.

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 shaded rankings 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. 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" on pages 2-3 of worksheet 12.

Step 3: Read fact sheet 8, Improving Animal Manure Storage, 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 Manure Storage Technical Reviewers: Ronald E. Hermanson, WSU Cooperative Extension; Andy Werkhoven, Dairy Farmer; Anne Schwartz, Washington Tilth; John A. Gillies, USDA-Soil Conservation Service; Philip A. KauzLoric, Washington Department of Ecology; John W. Bernard, WSU Cooperative Extension.

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.