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1.) The Corral Areas: Freestall corrals theoretically contribute a comparatively small volume of nitrogen to the underlying soil due to the concrete-lined flush system which transports wastes from these corrals. In addition, since these corrals will be covered, there is virtually no hydraulic head from rainfall or other sources which would drive the ammonium and nitrate molecules continually deeper into the soil. Although the loafing barns will not have stalls, they will also be covered, with flushed feed alleys. Three 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 should be sloped 4%to 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 tight silty clay material, infiltration and permeability is impeded. If ponding of water does occur in the open corrals, a sump pump may be used to transfer water into a drain and ultimately into the separation basins. The second factor reducing nitrate impact to the groundwater is the clay content of the soil down to 24 inches. The clay content percentage of a composite sample from grade to 24 inches was determined to be 26%by the hydrometer test, ASTM D422: Particle Size Analysis of Soils. The third mitigating factor of restricting downward migration of nitrogen in the open and loafing corrals is soil compaction from the animals. The hooves of the cows act essentially like a "shcepsfoot" soil compactor, creating a high density, low void space soil "cap" in the top six inches of the soil profile. Soil compaction attenuates the downward migration of nitrate molecules by reducing pore water permeability. 2.) Containment Structures: The wastewater system will consist of three separation basins and a holding pond. A certain percentage of nitrogen entering this system will volatilize in the form of ammonia(NH.) 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%. Ammonia volatilization occurs from urine and manure solids transfer to the ponds and during pond storage. All containment structures will be tested for clay content by the hydrometer method for compliance with liner requirements by the Regional Water Quality Control Board. The ponds can be considered predominately anaerobic. An aerobic environment is required for nitrate conversion to occur. Significant conversion can only take place when the pond and basins are allowed to dry out. When the manure is eventually cleaned-out or draglined, it should be done as soon as feasible after the water is pumped to impede nitrate conversion from occurring. 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 relatively low 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 valfey Aq PPsearch