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27 April 2020 <br />Project No. 20-5084 <br />Page 13 of 15 <br />RESIDENTIAL: <br /> <br />The Hantzsche / Finnemore (Nr) equation for residential home application: <br />Nr = I x Nw (1-d) + R x Nb ÷ (I+R) <br /> <br />Definitions: <br /> <br />Nr = The average concentration of nitrate-nitrogen in the recharged wastewater parts per <br />million of nitrate-nitrogen. <br /> <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 <br />150 gpd (existing system) + 150 gpd (proposed system) x 365 days of proposed operation <br />= (150 + 150) x 365 days ÷ 7.48 gallons per cubic foot = 14,639 cubic feet of wastewater. <br />Does not account for evapotranspiration likely to occur. <br /> <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 /> <br />d = Fraction of nitrogen concentration removed from the wastewater due to denitrification <br />within the soil (30 percent for clay loam soils). <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 Count y by the EHD. <br /> <br />EXISTING HOME AND PROPOSED HOME CALCULATIONS (COMBINED): <br /> <br />Nr = I x Nw (1-d)+ R x Nb ÷ (I+R)Assumptions: <br /> <br />I = 109,500 gallons = 14,639 cubic feet wastewater ÷ [(2.01 acres x 43,560 feet2) ÷ 12 <br />inches] = 2.00 inches/year <br />NW = 34.425 mg/L-N <br />d = 30 percent denitrification <br />R = 3.12 inches/year <br />Nb = 1.0 milligram per liter <br />Nr = [2.00 inches/year x 34.425 mg/L-N (1-0.30)] + (3.12 inches/year x 1.0 milligram per <br />liter) ÷ (2.00 inches/year + 3.12 inches/year) <br />Nr = 51.31 ÷ 5.12 = 10.0 <br />Nr = 10.0 ppm nitrogen (NO3_N)