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11 October 2019 AGE Project No. 19-4782 Page 13 of 14 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 RESIDENCE CALCULATIONS: Nr = I x Nw (1-d)+ R x Nb ÷ (I+R) Assumptions: I = 153,300 gallons = 20,495 cubic feet wastewater ÷ [(2.11 acres x 43,560 feet2) ÷ 12 inches] = 2.68 inches/year NW = 34.425 mg/L-N d = 15 percent denitrification R = 3.64 inches/year Nb = 1.0 milligram per liter Nr = [2.68 inches/year x 34.425 mg/L-N (1-0.15)] + (3.64 inches/year x 1.0 milligram per liter) ÷ (2.68 inches/year + 3.64 inches/year) Nr = 82.06 ÷ 6.32 = 12.98 Nr = 12.98 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, AGE does not anticipate percolating effluent will affect any nearby water sources. Based on the volume of wastewater to be generated, the potential vertical migration would not likely degrade the local groundwater. A total of 12.98 ppm of additional nitrogen is estimated to be added to the site over the long term through waste water recharge from the proposed septic system. The nitrogen loading value is above the desired value of 10 ppm. 10.0. TOTAL NITRATE IMPACT FROM PROPOSED PROJECT Based on the method and assumptions described, proposed NO3_N mass of wastewater and the calculations of the NO3_N loading predicted, the proposed development may negatively impact NO3_N loading rates within the aquifer. The soil at the site appear to be adequate for nitrate degradation and proper leaching of wastewater. A total of 12.98 ppm of additional nitrogen is estimated to be added to the site over the long term through waste water recharge from the proposed septic system.