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ced 12 October 2020 A Compony Geo Project No. 20-6164 ''~�� Page 13 of 15 250 gpd (existing system) + 200 gpd (proposed system)x 365 days of proposed operation = 450 x 365 days _ 7.48 gallons per cubic foot = 21,958 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 (40 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 = I x Nw (1-d)+ R x Nb T (I+R) Assumptions: I = 164,250 gallons = 21,958 cubic feet wastewater T [(2.0 acres x 43,560 feet2) _ 12 inches] = 21,958 . 7,260 = 3.02 inches/year NW = 34.425 mg/L-N d = 40 percent denitrification R = 3.69 inches/year Nb = 1.0 milligram per liter Nr = [3.02 inches/year x 34.425 mg/L-N (1-0.40)] + (3.69 inches/year x 1.0 milligram per liter) _ (3.02 inches/year + 3.69 inches/year) Nr = 66.07 = 6.71 = 9.85 Nr = 9.85 ppm nitrogen (NO3_N) 9.7. IMPACT OF NITROGEN LOADING FROM SITE PROJECT TO DOWNGRADIENT WATER SOURCES The recharging of groundwater is the most likely potential feature that could impact future nitrogen loading. Since the subject property is flat, AGI does not anticipate percolating effluent will affect any nearby water sources. Based on the volume of wastewater to be generated and the depth to groundwater (140-150 feet bsg), the potential vertical migration would not likely degrade the local groundwater. A total of 9.85 ppm of additional nitrogen is estimated to be added to the site over the long term through wastewater recharge from the proposed septic system. The nitrogen loading value is below the desired value of 10 ppm.