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flow from a single-family residence should be calculated as 100 gallons per day (gpd) for the first bedroom and 50 gpd for each additional bedroom; additional residences should be calculated in the same manner (personal communication, March 4, 2020). Using this method, the three-bedroom home will contribute 200 gpd, and the four- bedroom home will contribute 250 gpd. A typical residential concentration of 35 mg/L of nitrate as N was selected for the proposed residence (Crites and Tchobanoglous, 1998). The estimated flow values discussed here should not be used for the design and sizing of the septic system. The design and sizing of the septic system should utilize the San Joaquin County Environmental Health Department On-Site Wastewater Treatment Systems Standards, which incorporates peak and surge flow factors. The estimates used in the On-Site Wastewater Treatment Systems Standards may be greater than those discussed here. Denitrification Reductions Denitrification is a process that occurs in the septic system drain field whereby certain bacteria oxidize the nitrate (NO3) in the wastewater and release nitrogen gas (N2) to the atmosphere. Due to the biologic processes in the shallow soils, nitrogen in the drain field may undergo a reduction between 10 percent to 35 percent. Soils with higher clay content, moist soil conditions, high pH, and organic material denitrify by about 35 percent, and soils with high sand content tend to denitrify at a lower rate of about 10 percent. A typical denitrification factor of 25 percent was selected for the Site because of the mixed silt/sand/clay soil types present at the percolation test locations. Nitrate Loading Estimate A nitrate loading scenario was employed for each proposed new parcel to determine the impact from the minor subdivision to ground water. The scenario utilizes the variables discussed previously, which represent the estimated conditions and uses associated with this project. The following tables presents summaries of the assumptions for the nitrate loading calculations for each parcel of the Site, as presented in Plates 15 and 16. LOGE 2111 Page 12