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2.) Containment Structures: The wastewater system consists of a separation basin and a holding pond. A 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%. Ammonia volatilization occurs from urine, manure wastewater transfer to the ponds and during pond storage. Although both containment structures have not been hydrometer tested for clay content, from the indigenous high clay content soils, the structures are most likely in compliance with liner requirements of 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 if the ponds are allowed to dry out. When the manure in the basin and pond is eventually cleaned-out or draglined, it should be done as soon as feasible after the water is pumped to prevent this conversion from taking place. The second issue regarding the ponds 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. It has been documented that nitrate concentrations in groundwater around wastewater holding ponds is comparatively low in high clay content soils. 3.) Septic System Contribution: Data from various sources such as independent investigators, the U.S. EPA, and the Regional Water Quality Control Board estimate nitrogen loadings from domestic sewage from 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 50 gal/capita/day with an effluent concentration of 30-60 mg N/L. It is our opinion that 60 mg N/L is most accurate. The following calculations determine nitrate-nitrogen loading from septic contributions: 25 people max. on-site x 10 gals/day = 250 gals x 3.79 L/gal = 948 L/d x 60 mg N/L = 57 grms N/day x 365 days/yr=21 kg N/yr x 2.2 lb/kg =46 lbs N/yr. 4.) NITROGEN PRODUCTION CALCULATIONS The total nitrogen excreted from dairy animals is difficult to quantify since the rates of several important nitrogen transformation processes such as ammonia volatilization can only be predicted. The following calculations incorporate the use of animal units (AU)to formulate the nitrogen loading. The animal numbers are approximate and represent the projected number of animal types which will eventually move onto the home dairy. Presently, the animals at the home dairy are kept in corrals with scraped alleys. Additional freestalls are proposed for future expansion. 6 Vaffey Ag Ppearck