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29 May 2020 11.rt ancedGe0 Project No. 20-6014 e Owned Company Page 12 of 14 RESIDENTIAL: The Hantzsche / Finnemore (Nr) equation for residential home application.- Nr = I x Nw (1-d) + R x Nb . (I+R) pplication:Nr = IxNw (1-d) + RxNb = (I+R) Definitions: 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 (proposed system) x 365 days of proposed operation = 150 x 365 days _ 7.48 gallons per cubic foot = 7,319 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 silty sandy soils). R = Estimated Deep percolation / average rainfall recharge rate per year: 3.69 inches. Nb = Background nitrate-nitrogen concentration of rainfall recharge: 1.0 mg/l. The Nb is an average value determined for San Joaquin County by the EHD. PROPOSED HOME CALCULATIONS: Nr = IxNw (1-d)+ RxNb _ (I+R) Assumptions: I = 54,750 gallons = 7,319 cubic feet wastewater - [(0.228 acres x 43,560 fee t2) _ 12 inches] = 8.84 inches/year NW = 34.425 mg/L-N d = 25 percent denitrification R = 3.69 inches/year Nb = 1.0 milligram per liter Nr = [8.84 inches/year x 34.425 mg/L-N (1-0.25)] + (3.69 inches/year x 1.0 milligram per liter) _ (8.84 inches/year + 3.69 inches/year) Nr = 231.92 _ 12.53 = 18.50 Nr = 18.50 ppm nitrogen (NO3_N)