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Table 4. Results of Nitrate Loading Calculations Variable Value Units Description Nc, 2 bedrooms 9.6 mg/L-N Long-term average concentration of percolating effluent, 2-bedroom house Nc, 3 bedrooms 11.7 rng/L-N Long-term average concentration of percolating effluent, 3-bedroom house Nc, 4 bedrooms 13.3 mg/L-N Long-term average concentration of percolating effluent, 4-bedroom house The US EPA recommended MCL for nitrate in drinking water is 10 mg/L-N. In a worst- case situation, the maximum buildup of nitrates in the aquifer from the use of septic systems on the Site is predicted to be 9.6 mg/L-N for a two-bedroom house, 11.7 mg/L- N for a three-bedroom house, and 13.3 mg/L-N for a four-bedroom house. The result of the nitrate loading estimate is slightly below the maximum drinking water standard for a two-bedroom house, and slightly above for a three- or four-bedroom house. Discussion of Nitrate Loading Results Total Nitrate Impact Based on the method and assumptions described, the result of the nitrate loading estimate indicates that a two-bedroom house on the Site should not cause a buildup of nitrates in the aquifer above 10 mg/L-N; however, a three- or four-bedroom house may cause a buildup above 10 mg/L-N. There are three mitigating factors that should be considered, however, when evaluating whether or not this Site is likely to impact ground water with nitrate: The Hantzsche and Finnemore equation is a conservative method for determining potential impacts, and actual nitrate loading experienced on the Site over time may be less than predicted. The requirement by San Joaquin County Environmental Health Department that the calculation use rainfall and evapotranspiration data to determine ground-water recharge is particularly conservative, as it does not include consideration of recharge from irrigation water or surface water sources. The Site is located over 1,200 feet from its nearest residential neighbor. Substantial attenuation would be anticipated over the distance between the Site and its neighbors. LOGE 1909 Page 12