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rF nment. The nitrate loading potential of the subject facility originates from primarily four s: 1.) The corral areas - open corrals, covered loafing barns and the freestall barns. 2.) paration basins and wastewater holding pond, 3.) Septic system impacts and 4.)Nutrient ations to cropland. Each of the sources and their potential nitrate nitrogen concentration arescussed below: 1.) The Corral Areas: Freestall corrals theoretically contribute a 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 freestall. In addition, since these corrals will be 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. Although the loafing bams will not have stalls,they will also be covered, with flushed feed alleys. 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. Since the soil under the open corrals is composed of a clayey silt material, infiltration and permeability is impeded. The second and most important mitigating factor of restricting downward migration of nitrogen in the open corrals is the fact that Mr. Quaresma has imported co-gen fly ash and has lined each of the corrals with approximately one-foot of this material. This material will "set-up"after becoming wet to create very slow permeability properties, similar to concrete. 2.) Nutrient Containment Structures: The waste management system consists of three "cells" within one containment structure. 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(2000 ft x 80 ft) and significant reduction in nitrogen content should be achieved since the hydraulic retention time (HRT) is comparatively long. 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 and basins are allowed to dry out. When the manure is excavated or draglined from the first cell, it is done as soon as feasible after the water is pumped out to impede nitrate conversion (nitrification). 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 non-existent around wastewater holding ponds that are composed of high clay content soils. Because of the tight indigenous on- site soils, denitrification may be promoted. 6 Na&l y Ag Research