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04 November 2019 AdvancedGeo <br /> AGE Project No. 19-4819 Environmental <br /> Page 4 of 5 �- <br /> Nr = IxNW (1-d) + RxNb - (I+R) <br /> Definitions: <br /> Nr= The average concentration of nitrate-nitrogen in the recharged waste water parts per <br /> million of nitrate-nitrogen. <br /> I = Volume rate of wastewater entering the soil averaged over the gross developed area <br /> (acres) in inches per year. The total wastewater volume for proposed project will be 560 <br /> gpd (existing system) + 280 gpd (proposed system) x 365 days of proposed operation = <br /> (560 + 280) x 365 days - 7.48 gallons per cubic foot = 40,989 cubic feet of wastewater. <br /> Does not account for evapotranspiration likely to occur. <br /> NW = Total nitrogen concentration of wastewater at 45 mg/L-N based on the average <br /> discharge. Accounting for the loss of mg/L-N in the septic tank at 15% = 45-15%= 38.25 <br /> and the loss from the biomat at 10% 38.25 - 10% = 34.425 mg/L-N <br /> d = Fraction of nitrogen concentration removed from the wastewater due to denitrification <br /> within the soil (25% for silty clayey fine-grained sand soil). <br /> R = Estimated Deep percolation / average rainfall recharge rate per year: 3.12 inches. <br /> Nb = Background nitrate-nitrogen concentration of rainfall recharge: 1.0 mg/l. The Nb is <br /> an average value determined for San Joaquin County by the EHD. <br /> EXISTING HOME AND PROPOSED HOME CALCULATIONS (COMBINED): <br /> Nr = IxNw (1-d)+ RxNb = (I+R) <br /> Assumptions: <br /> I = 306,600 gallons = 40,989 cubic feet wastewater _ [(1.67 acres x 43,560 feet2) _ 12 <br /> inches] = 6.76 inches/year <br /> NW = 34.425 mg/L-N <br /> d = 25 percent denitrification <br /> R = 3.12 inches/year <br /> Nb = 1.0 milligram per liter <br /> Nr = [6.76 inches/year x 34.425 mg/L-N (1-0.25)] + (3.12 inches/year x 1.0 milligram per <br /> liter) _ (6.76 inches/year + 3.12 inches/year) <br /> Nr = 177.65 = 9.88 = 17.98 <br /> Nr = 17.98 ppm nitrogen (NO3_N) <br />