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Table 4. Assumptions for Nitrate Loading Calculation <br />Variable Value Units Description <br />Q 100 gpd Effluent flow rate <br />Nw <br />35 <br />mg/L-N <br />Effluent stream concentration <br />A <br />0.15 <br />acres <br />Site area <br />Nb <br />0.17 <br />mg/L-N <br />Concentration of rain <br />d <br />0.25 <br />constant <br />Denitrification factor <br />R <br />9.42 <br />inches per year <br />Recharge rate of rainfall <br />W 9.0 inches per year Uniform waste water loading (calculated) <br />The details of the nitrate loading calculation are included in Plate 13. 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 12.9 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 12.9 mg/L-N. The result of the nitrate loading <br />estimate slightly exceeds the maximum drinking water standard. <br />Discussion of Nitrate Loadina Results <br />Total Nitrate Impact <br />Based on the method and assumptions described, the result of the nitrate loading <br />estimate indicates that the proposed development on the Site has the potential to cause <br />a buildup of nitrates in the aquifer over 10 mg/L-N. <br />There are several mitigating factors that should be considered, however, when <br />evaluating whether or not the Site is likely to impact ground water with nitrate: <br />LOGE 2145 Page 12 <br />