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By using the ADF calculated above, the total nitrogen.theoretically produced by the proposed number of people on-site can be formulated for comparison with the nitrogen applied to the walnut orchard: 509 gals/day ADF x 3.79 L/gal = 1,929 L/day x 52 mg N/L (after reductions in nitrogen content) = 100 grams N/day x 314 days/yr = 31.5 kg N/yr x 2.2 lb/kg= 69.3 lbs N/yr_ 11 Acres = 6.3 lbs N/Ac/yr contributed from potential septic system impact. Even if there were no reductions assigned to the nitrogen content,this would increase the figure above to approximately 12.6 lbs N/Ac/yr. In comparison, Mr. Foppiano applies two, split applications of nitrogen at 50 units (50 lbs N/Ac) in the spring and mid-summer, for a total of 100 lbs N/Ac/yr. According to the Western Fertilizer Handbook, this is the correct amount to apply to walnut trees in their current stage of growth. Additionally, the nitrogen is applied in split applications so that the walnut trees can uptake and use the nitrogen at two separate times during the growing season. This reduces the likelihood that excess nitrogen will leach past the root zone. f C. SEPTIC SYSTEM COMPONENTS AND NITRATE IMPACT MITIGATION E The design of the proposed septic system should be based upon the factors of operation, longevity, I and environmental protection. The San Joaquin County Environmental Health Department will [ stipulate design requirements for these factors,particularly environmental protection. SEPTIC TANKS Septic tanks affect the sludge, scum and effluent volumes, which in turn affect treatment of nitrogen within the tanks. Typically, the volumetric capacity of septic tanks serving commercial ° facilities should be equal to approximately 5 times the Average Daily Flow(5 x 442 = 2210 gals). In the following equation, the numerical value for pump-out time interval in yrs, times the ADF, times the peaking value (PF), gives tank capacity required. The peaking value is normally taken to be 1.5 for commercial projects: SEPTIC TANK CAPACITY EXAMPLE FOR THE NEW RESTROOM: Recommended tank capacity for a pump out interval of three yrs: 2.4(QA„E) x Peaking Factor(PF) = 2.8(509) x 1.5 = 2,138 gal tank capacity required. there are two restrooms that can be used equally on a theoretical basis; therefore, use one - 2,000 gallon tank for the new septic system. r DETENTION TIME EXAMPLE FOR THE NEW RESTROOM: Detention Time= 2000 gal tank capacity x 0.70 30%volume lost to sludge/scum accumulation) 1.5 (Peaking factor) x 509 gals/day ^ Detention Time = 1.83 days. The minimum acceptable detention time is 1.0 day. 9 Vafiey AB Research t