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24 March 2020 AdvancedGeo An Employee•OwnedCompany Project No. 19-4964 _ Page 2 of 3 " Nr = The average concentration of nitrate-nitrogen in the recharged wastewater parts per million of nitrate-nitrogen. I = Volume rate of wastewater entering the soil averaged over the gross developed area (acres) in inches per year. The total wastewater volume for proposed project will be 150 gpd (existing system) + 200 gpd (proposed system) x 365 days of proposed operation = (150 + 200) x 365 days - 7.48 gallons per cubic foot = 17,079 cubic feet of wastewater. Does not account for evapotranspiration likely to occur. NW = Total nitrogen concentration of wastewater at 45 mg/L-N based on the average discharge. Accounting for the loss of mg/L-N in the septic tank at 15% = 45-15%= 38.25 and the loss from the biomat at 10% 38.25 - 10% = 34.425 mg/L-N. d = Fraction of nitrogen concentration removed from the wastewater due to denitrification within the soil (25 percent for sandy loam soils). R = Estimated Deep percolation / average rainfall recharge rate per year: 3.64 inches. Nb = Background nitrate-nitrogen concentration of rainfall recharge: 1.0 mg/I. The Nb is an average value determined for San Joaquin County by the EHD. PROPOSED HOME CALCULATIONS: Nr = I x Nw (1-d)+ R x Nb - (I+R) Assumptions: I = 127,750 gallons = 17,079 cubic feet wastewater - [(3.0 acres x 43,560 feet2) - 12 inches] = 1.57 inches/year NW= 34.425 mg/L-N d = 25 percent denitrification R = 3.64 inches/year Nb = 1.0 milligram per liter Nr = [1.57 inches/year x 34.425 mg/L-N (1-0.25)] + (3.64 inches/year x 1.0 milligram per liter) - (1.57 inches/year + 3.64 inches/year) Nr = 44.18 = 5.21 = 8.48 Nr = 8.48 ppm nitrogen (NO3_N) A total of 8.48 ppm of additional nitrogen is estimated to be added to the site over the long term through wastewater recharge from the proposed septic system.