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Quantity and Quality of Domestic Wastewater <br /> Ms. Gomez indicated that a two-bedroom modular home will be placed on the Site. <br /> Crites and Tchobanoglous (1998) list a typical flow rate of 50 to 70 gallons per person <br /> per day for an individual residence. The San Joaquin County Environmental Health <br /> Department has indicated that maximum flow and double occupancy within each <br /> 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 280 allons per day (gpd), <br /> based on two 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 (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 will may undergo a reduction between 10 percent to 35 percent. Soils with higher <br /> clay 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 o 35 percent was selected for the Site because of the clay soil <br /> present at the percolation test location. <br /> Nitrate Load ing_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 1920 Page 10 <br />