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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 is the removal of manure from the corrals before the rainy season to alleviate the percolation of nitrogen. Secondly, the open �. corrals are sloped to expedite rainwater runoff. Each corral is sloped 6% from the center to the ends to promote rainwater runoff into the containment separation basins. This water management technique reduces percolating water through the soil profile, thus preventing hydraulic head pressures. Since the soil under the open corrals is composed of a clayey silt material, infiltration and permeability is impeded in comparison to a sandier soil structure. 2.) Nutrient Containment Structures: The second issue regarding the containment structures is the natural process of immobilization and 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. Because of the fine-grained indigenous on-site soils (clay loam), ammonium retention may be enhanced within the clay latices, leading to immobilization. Nitrate that does form through nitrification may be readily denitrified. 3.) Silage Storage Areas: Silage liquor runoff from the Home Ranch asphalt-lined silage bunkers is captured by a sump and a pipeline transfers the runoff across the entrance driveway and into the holding pond. Consequently, there is no runoff onto and into the soil. The silage storage at the Acampo Ranch is on bare ground, with silage liquor runoff captured by the secondary pond adjacent to the north of the silage bunker. 4.) Septic System Contributions: Data from various sources including independent investigators, the U.S. EPA, and the Regional Water Quality Control Board estimate nitrogen loadings from domestic sewage to be 12 grams N per person per day (g N/capita/day)to a high of 90 g N/capita/day. Hantzche and Finnemore (1992) correlated septic tank effluent concentrations multiplied by water discharge to the septic tank. They formulated a water discharge of 100 gal/capita/day with an effluent concentration of 30-60 mg N/L. 60 mg N/L is a conservative estimate for this type of operation. The following calculations determine nitrate-nitrogen loading from septic system contributions at the Home Ranch: 12 on-site employees x 100 gals/day = 1,200 gals x 3.79 L/gal=4,548 L/d x 60 mg N/L = 273 grms N/day x 365 days/yr= 100 kg N/yr x 2.2 lb/kg=220 lbs N/yr. This impact is negligible in comparison to the amount of nitrogen produced by the dairy facility and used by the associated cropland. 5.) Nutrient Applications Areas: Nutrients applied to the cropland have been quantified in the Nutrient and Irrigation Water Management Plans (NIWMPs). Cropland accepting bovine nutrients can be the most critical area for preventing groundwater and surface water contamination. Therefore, as discussed in the Conclusion Section of this Technical Report, analyses should be done on the following media to adequately assess nutrient loading: Cropland soil, irrigation water, nutrient water and the blend of Beaver Slough irrigation water with nutrient water immediately before land application. An analysis of a blend of Beaver Slough irrigation water and nutrient holding pond water was not possible for this Technical Report since no irrigation blend occurred during the study. Both clean irrigation water sources (Beaver Slough and " Home Ranch irrigation well) were analyzed individually, however, and are noted in Table 9. The following Table 10 illustrates the analysis of the nutrient water in the holding pond. The sample was obtained from the flush pump discharge, which pumps from the pond surface. -18- Chesnq Consulting