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20 November 2020 Advanced Project No. 20-6205 AnEmployee-Owned Company Page 12 of 14 9.6. MASS BALANCE OF NITROGEN LOADING The EHD requires the user to consider all potential sources identified for wastewater generation. Further, the EHD supports the use of Hantzsche/Finnemore, or other appropriate formula/model to calculate a mass of nitrogen loading. RESIDENTIAL: The Hantzsche / Finnemore (Nr) equation for residential home application: 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 250 gpd (proposed system) x 365 days of proposed operation = 250 x 365 days - 7.48 gallons per cubic foot = 12,199 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 (30 percent for loamy 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/I. The Nb is an average value determined for San Joaquin County by the EHD. EXISTING AND PROPOSED HOME CALCULATIONS: Nr = IxNw (1-d)+ RxNb = (I+R) Assumptions: I = 91,250 gallons = 12,199 cubic feet wastewater - [(0.5 acres x 43,560 feet2) - 12 inches] = 12,199 _ 1,815 = 6.72 inches/year NW = 34.425 mg/L-N d = 30 percent denitrification R = 3.69 inches/year Nb = 1.0 milligram per liter