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LBA Realty <br /> Draft Soil Suitability and Nitrate Loading Study <br /> 4.4.1. Expected On-Site Septic System Demands <br /> Septic system demands were estimated using the LEED estimate for employees per building. Based on <br /> conversations with the EHD, it was determined that each employee contribute 7.5 gallons per day of waste <br /> because the developer is installing low flow fixtures. Based on the average daily flow per building the septic tank <br /> and leach field were designed using the San Joaquin County Onsite Wastewater Treatment Systems Standard <br /> (San Joaquin County Ordinance Code Section 9-1105). See Attachment 5 for the tabulated calculations of the <br /> septic system sizing. <br /> For the purposes of this study the demand of the entire site is used to determine the Nitrogen Loading.The total <br /> effluent sewer is estimated to be 2,025 gallons per day. As stated above, a value of 50 mg/I as Nitrate was used <br /> for this study. <br /> 4.5. Mass Balance of Nitrogen Loading <br /> A nitrate loading analysis was performed to determine the impact of onsite wastewater treatment systems from <br /> the project to local ground water. <br /> Denitrification is a process that occurs in the septic system leach field where bacteria metabolize the oxygen in <br /> nitrate in the wastewater and release nitrogen gas to the atmosphere. Based on the conditions of the soil in, <br /> and underlying, the leach field a reduction of 10-25%will take place. For the purposes of this study a reduction <br /> of 17.5%will be used. <br /> The nitrate loading study will use the assumptions discussed above. Attachment 6 provides a summary of the <br /> assumptions and calculations used for the nitrate loading calculations. <br /> The results of the nitrate loading,or long-term average concentration of percolating effluent,as calculated using <br /> the Hantzsche and Finnemore equation are presented below. <br /> Table 1—Result of Nitrate Loading Calculation <br /> Variable Value Units Description <br /> N 7.96 Mg/L-N Long-term average concentration of percolating effluent <br /> November 30, 2020 4-2 Schaaf & Wheeler <br /> CONSULTING CIVIL ENGINEERS <br />