Collection and Storage of Agricultural Animal Wastes and Wastewater: Fact Sheet

• Risks from Animal Wastes
• Location of Wells, Livestock Yards, and Soil Characteristics
• Protecting Your Groundwater
• Runoff Control Systems
• Best Management Practices
• Dry Lots versus Liquid Handling Systems
• Safety
• Waste Management Plan

Risks from Animal Wastes

Design and construction of waste collection and storage systems must be adequate to handle normal runoff as well as extreme rainfall events. If not designed correctly, nitrate found in animal waste can contaminate local water supplies.

High concentrations of nitrate in drinking water can affect your health. The federal and state drinking water level for nitrate (measured as nitrate-nitrogen) is 10 milligrams per liter. Levels above this are considered unsafe. Infants and certain elderly people are the most susceptible to nitrate in water. When these individuals drink water or eat foods that contain high nitrate levels, their blood can lose the ability to effectively carry oxygen. This condition is called "methemoglobinemia" or "blue baby syndrome". Although the condition can be fatal if not diagnosed quickly, it is easily reversed with medical treatment. Livestock are also susceptible to health problems from high nitrate levels.

Location of Wells, Livestock Yards, and Soil Characteristics

Wells should be located in elevated areas, upslope from livestock yards. Wells should never be sited in areas prone to flooding.

Soil characteristics are very important when considering where to locate a livestock yard. Soil texture, depth to water table, and infiltration rates affect the susceptibility of groundwater to contamination.

Poor sites have shallow soils or a high water table. Sandy or gravelly soils with excessive drainage and high infiltration rates are also poor sites for livestock yards.

The best sites have deep clay or clay loam soils, with low infiltration rates. If your livestock yard is located on sandy soils, you can provide liquid-tight basins to store yard runoff.

Protecting Your Groundwater

There are measures you can take to reduce the potential of nitrate from contaminating your groundwater supplies. One of the most important things to remember is to keep all clean water that enters your property clean, and to manage your wastewater.

Waterways, small berms, and roof gutters can all be used to direct water away from livestock yards. An earthen berm can be built across the slope, upgrade from a livestock yard, to prevent clean runoff from entering the yard. If a berm is not practical, a catch basin with a tile outlet can be installed above the yard.

Polluted runoff from the yard should be collected and channeled to an area where it will have minimal effect on surface water or groundwater.

Runoff Control Systems

The absence of runoff controls in a CAFO can lead to water quality problems. Contaminated runoff can seep down into the groundwater supply, especially if the soil is sandy and drains easily.

Runoff control systems can remedy such problem situations. These systems collect runoff, settle out manure solids, and direct the remaining water to open fields or filter strips, away from streams, ditches, waterways, and areas of permeable soils and creviced bedrock. Another option is to collect and store runoff for later land application.

Best Management Practices

Under current law, all CAFO operators have a General Agricultural Aquifer Protection Permit. No application is needed to receive this permit. As long as operators follow the mandated BMPs and can show which GPs were employed to attain the BMP goals, they retain the general permit.

The BMPs for CAFOs must be met by the owners/operators to minimize the discharge of nitrogen pollutants from their facilities.

The three mandated BMPs for CAFOs are:

BMP 1--Harvest, stockpile and dispose of animal manure from a CAFO to minimize discharge of nitrogen pollutants by leaching and runoff.

BMP 2--Control and dispose of nitrogen-contaminated water resulting from activities associated with a CAFO, up to a 25-year, 24-hour storm event equivalent to minimize the discharge of nitrogen pollutants.

BMP 3--Close facilities in a manner to minimize the discharge of nitrogen pollutants.

Guidance Practices are methods used to achieve BMP goals. For example, the application of animal waste to croplands is one GP for the first BMP. Other GPs include diverting water that originates outside a facility from running onto the facility; diverting clean runoff from buildings away from facility pens; and designing and constructing storage ponds to contain liquid waste runoff from lots and pens.

The 25-year, 24-hour storm event equivalent in BMP 2 refers to a "design storm", one that probably will occur only four times in any given 100-year period. A facility must be designed so that it does not discharge runoff to surface navigable waters in any storm event that is less than the size and length of a design storm.

Dry Lots versus Liquid Handling Systems

Wastes from CAFOs are handled as either solids or liquids. Liquid waste handling systems are found mainly on dairies and swine farms. Cattle feedlots, nonflushed dairy pens or corrals, nonflushed swine farms, poultry operations, sheep and goat corrals, and horse stables have solids-dominated waste.

Dry lots include corrals, holding pens not being washed, and nonflushed feed lanes. Important aspects of dry lot waste management include

a. handling and storage of solid wastes;

b. proper corral/pen sealing against groundwater contamination;

c. containment of rainfall runoff; and

d. protection of the dry lot from run-on water.

Swine farms and dairies need liquid handling systems to take care of the wastewater produced from the washing and flushing of pens, feed lanes, and holding areas. The liquids are usually conveyed to a central receiving and storage location, either to a lagoon (anaerobic) or a pond (aerobic). Wastewater contained in lagoons can either be applied to cropland or evaporated. Aerobic ponds primarily serve only as evaporation ponds. Important aspects of liquid-handling systems include

a. location of the waste ponds with respect to soil types (for groundwater protection);

b. location of the waste ponds with respect to potential flood zones (surface water protection);

c. adequate size of the waste conveyance and storage structures;

d. lining of waste storage structures to prevent deep percolation; and

e. protection of waste structures from rainfall run-on water.

Liquid-handling systems often have a solid separator to pull nonvolatile solids from the liquid, which are then handled by the solid-handling system.

Safety

Safety precautions are necessary when working around steep-sided ponds and lagoons. No one wants to run the risk of falling into a pond or lagoon and coming into contact with contaminated materials or drowning.

Entering nonvented, enclosed storage vessels for cleaning or maintenance poses the hazard of breathing in noxious gases. Some manure by-products (hydrogen sulfide and ammonia) can cause asphyxiation in relatively low concentrations. Hydrogen sulfide and methane are also flammable. Poultry and swine operations, often have enclosed storage areas. Make sure these areas are properly ventilated.

It is recommended that fences, barriers, and warning signs be posted throughout the storage area.

Waste Management Plan

Under state law, facility owners/operators must follow BMPs. It is equally important to be able to document how and where BMPs have been implemented. A waste management plan is a written statement that provides the needed documentation.

Facility expansion and other changes in operations can be addressed in a waste management plan. Prior to facility expansion, it is important to determine whether there is enough land for application of wastes; whether the treatment ponds and storage areas are large enough; and whether there is adequate run-on/runoff control.

Waste management plans should contain the following basic elements:

1. Drawing of the facility's capital structures showing surrounding elevations and location of any water courses, dry or not;

2. Location of the 100-year floodplain with respect to the facility;

3. Any calculations made of the amount of run-on/runoff water that must be contained;

4. Any calculations made of solid and liquid wastes generated by the animals that must be managed, and any projected increase in animal numbers;

5. Sizes of the capital structures of the waste management system and the amount of wastes they are calculated to handle (berms, conveyance pipes or canals, solid separators, lagoons or ponds, and farmland for nutrient-enriched wastewater applications);

6. Methods that will be used to minimize nitrate movement if the facility should be closed or sold; and

7. Information on proper use of the wastes on cropland, on well water quality, on other matters pertinent to proper waste management as well as information from soil surveys.

Arizona
Dept. of
Agriculture