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A denitrification factor of 35 percent was selected for the Site because of the clayey soil <br />present at the percolation test location and indicated by the Soil Survey. <br />Nitrate Loading Estimate <br />A nitrate loading scenario was employed to determine the impact from the proposed <br />project to ground water. The scenario utilizes the variables discussed previously, which <br />represent the estimated conditions and uses associated with this project. The following <br />table presents a summary of the assumptions for the nitrate loading calculation for the <br />Site, as presented in Plate 14. <br />Table 4. Assumptions for Nitrate Loading Calculation <br />Variable Value Units Description <br />Q 500 gpd Effluent flow rate <br />Nw 35 mg/L-N Effluent stream concentration <br />A 3.12 acres Site area <br />Nb 0.136 mg/L-N Concentration of rain <br />d 0.35 constant Denitrification factor <br />R 5.74 inches per year Recharge rate of rainfall <br />W 2.2 inches per year Uniform waste water loading (calculated) <br />The details of the nitrate loading calculation are included in Plate 14. The results of the <br />calculation are presented in the following table. <br />Table 5. Result of Nitrate Loading Calculation <br />Variable Value Units Description <br />Nc 6.3 mg/L-N Long-term average concentration of percolating effluent <br />The US EPA recommended MCL for nitrate in drinking water is 10 mg/L-N. In a worst- <br />case situation, the maximum buildup of nitrates in the aquifer from the use of septic <br />systems on the Site is predicted to be 6.3 mg/L-N, well below the maximum drinking <br />water standard. <br />LOGE 2203 Page 12 <br />