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The estimated flow values discussed here should not be used for the design and sizing <br /> of the septic system. The design and sizing of the septic system should utilize the San <br /> Joaquin County Environmental Health Department On-Site Wastewater Treatment <br /> Systems Standards which incorporate peak and surge flow factors. The estimates used <br /> in the On-Site Wastewater Treatment Systems Standards may be greater than those <br /> discussed here. <br /> Denitrification Reductions <br /> Denitrification is a process that occurs in the septic system drain field whereby certain <br /> bacteria oxidize the nitrate (NO3) in the wastewater and release nitrogen gas (N2) to the <br /> atmosphere. Due to the biologic processes in the shallow soils, nitrogen in the drain <br /> field may undergo a reduction between 10 percent to 35 percent. Soils with higher clay <br /> content, moist soil conditions, high pH, and organic material denitrify by about 35 <br /> percent, and soils with high sand content tend to denitrify at a lower rate of about 10 <br /> percent. <br /> A denitrification factor of 35 percent was selected for the Site because of the clayey soil <br /> present at the percolation test location. <br /> Nitrate Loading Estimate <br /> Two nitrate loading scenarios were employed to determine the impact from the <br /> proposed project to ground water: one scenario for two new houses, and the second <br /> scenario for three new houses. The scenarios utilize the variables discussed <br /> previously, which represent the estimated conditions and uses associated with this <br /> project. The following table presents a summary of the assumptions for the nitrate <br /> loading calculations for the Site, as presented in Plates 13 and 14. <br /> LOGE 20-08 Page 10 <br />