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07 Septmber 2021 <br />Project No. 21-6531 <br />Page 13 of 14 <br />Assumptions: <br />I = 146,000 gallons = 19,518 cubic feet wastewater ÷ [(2.5 acres x 43,560 feet2) ÷ 12 <br />inches] = 19,518 ÷ 9,075 = 2.15 inches/year <br />NW = 34.425 mg/L-N <br />d = 30 percent denitrification <br />R = 3.20 inches/year <br />Nb = 1.0 milligram per liter <br />Nr = [2.15 inches/year x 34.425 mg/L-N (1-0.30)] + (3.20 inches/year x 1.0 milligram per <br />liter) ÷ (2.15 inches/year + 3.20 inches/year) <br />Nr = 55.01÷ 5.35 = 10.28 <br />Nr = 10.28 ppm nitrogen (NO3_N) <br /> <br /> <br />9.7. IMPACT OF NITROGEN LOADING FROM SITE PROJECT TO <br />DOWNGRADIENT WATER SOURCES <br /> <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 (120 feet bsg), the potential vertical migration <br />would not likely degrade the local groundwater. A total of 10.28 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 slightly above the desired value <br />of 10 ppm. <br /> <br /> <br />10.0. TOTAL NITRATE IMPACT FROM PROPOSED PROJECT <br /> <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 soil at the site appear to <br />be adequate for nitrate degradation and proper leaching of wastewater. A total of <br />10.28 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 /> <br /> <br />11.0. MITIGATION METHODS PROPOSED <br /> <br />To mitigate any known or potential future impacts of nitrate to soil and groundwater from <br />the proposed septic system, the following mitigations could be implemented: <br /> <br /> Maximize wastewater hold time where practical (retention).