Laserfiche WebLink
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 />2.0 <br />acres <br />Site area <br />Nb <br />0.136 <br />mg/L-N <br />Concentration of rain <br />d <br />0.25 <br />constant <br />Denitrification factor <br />R <br />8.41 <br />inches per year <br />Recharge rate of rainfall <br />W 2.7 inches per year Uniform waste water loading (calculated) <br />The details of the nitrate loading calculation are included in Plate 14. The result of the <br />calculation is presented in the following table. <br />Table 5. Result of Nitrate Loading Calculation <br />Variable Value Units Description <br />Nc 6.5 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 6.5 mg/L-N for existing house and a potential <br />future second unit dwelling on the homesite parcel. The result of the nitrate loading <br />estimate is well below maximum drinking water standard. <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 potential future development on the Site should <br />not cause a buildup of nitrates in the aquifer over 10 mg/L-N. It should be noted that <br />nitrate levels beneath the Site are already well above the MCL, based on the water <br />samples collected from the domestic and irrigation wells. <br />LOGE 2124 Page 13 <br />