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(author of the 1992 paper discussed previously). He indicated that wastewater flow <br /> from a single-family residence should be calculated as 100 gallons per day (gpd) for the <br /> first bedroom and 50 gpd for each additional bedroom; additional residences should be <br /> calculated in the same manner (personal communication, March 4, 2020). <br /> Using this method, the potential future four-bedroom home on each parcel yields a <br /> calculated flow of 250 gpd. <br /> A typical residential concentration of 35 mg/L of nitrate as N was selected for the <br /> existing and future homes (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 incorporates peak and surge flow factors. The estimates <br /> used in the On-Site Wastewater Treatment Systems Standards may be greater than <br /> those 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 standard denitrification factor of 25 percent was selected for the Site because of the <br /> mixed silt and sand soil types observed at the percolation test locations. <br /> Nitrate Loading Estimate <br /> A nitrate loading scenario was employed to determine the impact from the future homes <br /> 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 19. <br /> LOGE 2217 Page 13 <br />