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{ S. SPECIFIC NITROGEN SOURCE CONSIDERATIONS The investigative factors of any nitrate source identification procedure involves the assessment of the site, to inventory and identify all potential nitrate sources. This Study identifies all on-site nitrogen sources which may contribute a certain percentage of the total amount of nitrate to the environment. The nitrate loading potential of the subject facility may originate from four sources: 1.) The corral areas - open corrals, covered loafing barns and the freestall barns. 2.) The nutrient water holding pond, 3.) Septic system impacts and 4.)Nutrient applications to cropland. Each of the sources and their potential nitrate nitrogen concentration are discussed below: 1.) The Corral Areas: Freestall corrals theoretically contribute a very small volume of nitrogen to the underlying soil due to the concrete-lined flush system which transports wastes from these corrals and very little waste from the cow is deposited within the actual freestall. In addition, since these corrals are covered,there is virtually no hydraulic head from rainfall or other water sources which could drive the ammonium and nitrate molecules continually deeper into the soil. Two factors are of significant importance to nitrogen contribution and the mitigation of the potential for nitrate impact from the open corrals. The first mitigating factor concerns the sloping of the open corrals to manage rainwater runoff. Each corral is sloped 6% from the center to the ends to promote rainwater runoff into a sump. This water management technique reduces percolating water through the soil profile by preventing hydraulic head. Secondly, since the soil under the open corrals is composed of a clayey silt material, infiltration and permeability are impeded in comparison to a sandy soil structure. 2.) Nutrient Containment Structure: As referenced above,the waste management system currently consists of one holding pond that serves both as solid/liquid separation and storage. A certain percentage of nitrogen entering this system will volatilize in the form of ammonia(NH3) or be adsorbed onto the clay soil particles lining the ponds as ammonium (NH4). An investigation by Sutton, (1983) suggests that a nitrogen loss from a holding pond system can range from 70%to 80%. The containment structure is long and narrow(800 ft x 100 ft) and significant reduction in nitrogen content should be achieved since the hydraulic retention time (HRT) is comparatively long (> 30 days). The ponds can be considered predominately anaerobic. An aerobic environment is required for ammonium conversion to nitrate to occur. Conversion can only take place when the pond is allowed to dry out. The second issue regarding the containment structures is the natural process of denitrification. This process takes place only in anaerobic environments such as saturated clay soils where the pore space volume is extremely small and pore space oxygen is readily consumed. It has been documented that nitrate concentrations in groundwater are low-to- nonexistent around wastewater holding ponds that are composed of high clay content soils. ' 3.) Silage Production and Storage Leachate runoff from silage storage areas, also referred to as silage liquor or silage juice, can be a nitrogen threat to groundwater quality. Three silage storage areas exist at the Dairy. One pad is completely concreted, and the other two pads are approximately one-half concrete and one-half soil lined. The silage pits have tight covers to prevent rainfall intrusion and increase silage ' leachate runoff. In addition, all leachate and rainfall runoff is collected into a sump that pumps the liquid to the existing holding pond, thus decreasing infiltration potential. 10 , f Chesney Consufting