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bedroom should be considered for the nitrate loading assessment; as a result, a value <br />of 140 gallons per bedroom per day has been selected (personal communication, <br />January 6, 2017). <br />The maximum daily flow for the Site was estimated to be 420 gallons per day (gpd), <br />based on three bedrooms at 140 gallons per bedroom. <br />A typical residential concentration of 35 mg/L of/nitrate as N was selected for the <br />proposed residence (Crites and Tchobanoglous(1998). <br />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 (NO 3) 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 standard denitrification factor of 25 percent was selected for the Site because of the <br />silt content of the soil present at the percolation test location. <br />Nitrate Loading Estimate <br />A nitrate loading scenario was employed to determine the impact from the proposed <br />project to ground water. The scenario utilizes the variables discussed previously, which <br />represent the estimated conditions and uses associated with this project. The following <br />table presents a summary of the assumptions for the nitrate loading calculation for the <br />Site, as presented in Plate 16. <br />LOGE 1924 Page 10