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Table 4. Assumptions for Nitrate Loading Calculation <br />Variable <br />Value <br />Units <br />Description <br />Q <br />400 <br />gpd <br />Effluent flow rate <br />Nw <br />35 <br />mg/L-N <br />Effluent stream concentration <br />A <br />0.96 <br />acres <br />Site area <br />Nb <br />0.136 <br />mg/L-N <br />Concentration of rain <br />d <br />0.35 <br />constant <br />Denitrification factor <br />R <br />2.67 <br />inches per year <br />Recharge rate of rainfall <br />W <br />5.6 <br />inches per year <br />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 15.4 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 15.4 mg/L-N. <br />Discussion of Nitrate Loading Results <br />Total Nitrate Impact <br />Based on the method and assumptions described, the result of the nitrate loading <br />estimate indicates that the existing and proposed development on the Site has the <br />potential to cause a buildup of nitrates in the aquifer above 10 mg/L-N. <br />There are several mitigating factors that should be considered, however, when <br />evaluating the degree to which the Site is likely to impact ground water with nitrate: <br />LOGE 2204 Page 13 <br />