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20 July 2021 AdvancedGeo <br /> Project No. 21-6486 An Employee-Owned Compony <br /> Page 14 of 15 � <br /> Nb = Background nitrate-nitrogen concentration of rainfall recharge: 1.0 mg/I. The Nb is <br /> an average value determined for San Joaquin County by the EHD. <br /> EXISTING AND PROPOSED HOME CALCULATIONS: <br /> Nr = I x Nw (1-d) + R x Nb = (I+R) <br /> Assumptions: <br /> I = 255,500 gallons = 34,158 cubic feet wastewater - [(3.03 acres x 43,560 feet2) _ 12 <br /> inches] =34,158 _ 10,999 = 3.10 inches/year <br /> NW = 34.425 mg/L-N <br /> d = 20 percent denitrification <br /> R = 3.20 inches/year <br /> Nb = 1.0 milligram per liter <br /> Nr = [3.10 inches/year x 34.425 mg/L-N (1-0.20)] + (3.20 inches/year x 1.0 milligram per <br /> liter) - (3.10 inches/year + 3.20 inches/year) <br /> Nr = 88.57 _ 6.30 = 14.05 <br /> Nr = 14.05 ppm nitrogen (NO3_N) <br /> 9.7. IMPACT OF NITROGEN LOADING FROM SITE PROJECT TO <br /> DOWNGRADIENT WATER SOURCES <br /> The recharging of groundwater is the most likely potential feature that could impact future <br /> nitrogen loading. Since the subject property is flat, AGI does not anticipate percolating <br /> effluent will affect any nearby water sources. Based on the volume of wastewater to be <br /> generated and the depth to groundwater (75 feet bsg), the potential vertical migration <br /> would not likely degrade the local groundwater. A total of 14.05 ppm of additional nitrogen <br /> is estimated to be added to the site over the long term through wastewater recharge from <br /> the proposed septic system. The nitrogen loading value is above the desired value of <br /> 10 ppm. <br /> 10.0. TOTAL NITRATE IMPACT FROM PROPOSED PROJECT <br /> Based on the method and assumptions described, proposed NO3_N mass of wastewater <br /> and the calculations of the NO3_N loading predicted, the proposed development may <br /> negatively impact NO3_N loading rates within the aquifer. The soils at the site appear to <br /> be adequate for nitrate degradation and proper leaching of wastewater. A total of <br /> 14.05 ppm of additional nitrogen is estimated to be added to the site over the long term <br /> through wastewater recharge from the proposed septic system. <br />