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LOGE 1844: Farris NLS Addendum 2 Page 2 <br /> March 21, 2019 <br /> The following table presents a summary of the assumptions for, and results of, the <br /> nitrate loading calculation for the Site when recharge is derived by the <br /> evapotranspiration reduction method with CIMIS data. A modified version of this <br /> method is currently being developed by the San Joaquin County Environmental Health <br /> Department for use in future studies. Details of the calculation are presented in Plate 2. <br /> Table 1. Inputs and Results for Nitrate Loading Calculation, <br /> Recharge Derived from Evapotranspiration Reduction Method <br /> Variable Value Units Description <br /> Q 420 gpd Effluent flow rate <br /> Nw 35 mg/L-N Effluent stream concentration <br /> A 1.50 acres Site area <br /> Nb 1.00 mg/L-N Concentration of rain <br /> d 0.20 constant Denitrification factor <br /> R 3.64 inches per year Recharge rate of rainfall <br /> W 3.8 inches per year Uniform waste water loading (calculated) <br /> Nc 14.7 mg/L-N Long-term average concentration of percolating <br /> effluent <br /> For this Site, the long-term average concentration of percolating effluent is found to be <br /> 14.7 mg/L-N when calculated as shown. This value exceeds the US EPA <br /> recommended MCL for nitrate in drinking water of 10 mg/L-N. <br /> There are several mitigating factors that should be considered, however, when <br /> evaluating whether or not this Site is likely to impact ground water with nitrate: <br /> • The map of Nitrate — Land Use Data (2019) prepared by San Joaquin County <br /> Environmental Health Department indicates that, within a half-mile radius <br /> surrounding the Site, one well has been tested for nitrate. Nitrate was detected <br /> over 10 mg/L in that well. Within a one-mile radius, however, four additional <br /> wells were tested, none of which were found to contain nitrate over 10 mg/L <br /> (Plate 3). <br /> • The surrounding area largely consists of orchards, with only occasional rural <br /> residences. It is well known that nitrate contamination in Ripon originates from <br /> agricultural fertilizer application. Agricultural programs are in place to assist with <br /> correct fertilizer application rates. <br /> • Additionally, depth to ground water beneath the Site is estimated to be 57 to 64 <br /> feet, as discussed in the original report. San Joaquin County experienced its <br />