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Table 4. Assumptions for Nitrate Loading Calculations <br /> Variable Value Units Description <br /> Q 250 gpd Effluent flow rate, 4-bedroom home <br /> Nw 35 mg/L-N Effluent stream concentration <br /> A 2.0 acres Site area (per proposed new parcel) <br /> Nb 0.136 mg/L-N Concentration of rain <br /> d 0.25 constant Denitrification factor <br /> R 3.21 inches per year Recharge rate of rainfall <br /> W 1.7 inches per year Uniform waste water loading (calculated) <br /> The details of the nitrate loading calculation are included in Plate 19. The results of the <br /> calculation are presented in the following table. <br /> Table 5. Results of Nitrate Loading Calculations <br /> Variable Value Units Description <br /> Nc 9.1 mg/L-N Long-term average concentration of percolating effluent <br /> Based on the methods and assumptions described, the use of proposed septic tanks <br /> and drain field systems on the Site yields a calculated buildup of nitrates in the aquifer <br /> up to 9.1 mg/L-N. <br /> The US EPA recommended MCL for nitrate in drinking water is 10 mg/L-N. The results <br /> of the nitrate loading calculation fall below the maximum drinking water standard. It <br /> should be noted, however, that existing nitrate level at the domestic well slightly <br /> exceeds the MCL. <br /> Discussion of Nitrate Loading Results <br /> Total Nitrate Impact <br /> Based on the method and assumptions described, the results of the nitrate loading <br /> estimate indicate that the proposed development on the Site should not cause a buildup <br /> of nitrate in the aquifer over 10 mg/L-N. As a result, nitrate mitigation is not <br /> recommended at this time. <br /> LOGE 2217 Page 14 <br />