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There are mitigating factors that should be considered, however, when evaluating the <br /> degree to which the Site is likely to impact ground water with nitrate: <br /> • The Hantzsche and Finnemore equation is a conservative method for <br /> determining potential impacts. The requirement by San Joaquin County <br /> Environmental Health Department that the calculation use rainfall and <br /> evapotranspiration data to determine ground-water recharge is particularly <br /> conservative, as it does not include consideration of recharge from irrigation <br /> water or surface water sources. <br /> • Depth to ground water beneath the Site is estimated to be approximately 35 to 40 <br /> feet, and only shallow septic systems are typically permitted in this area. Given <br /> these conditions, the vadose zone of the new septic system will be at least 25 <br /> feet, and significant nitrate attenuation would be anticipated over the course of <br /> this span. <br /> • Nitrate was detected at 6.5 mg/L-N, well below the MCL, in the on-site domestic <br /> well, despite the presence of an existing home on the Site. According to the map <br /> reviewed, none of wells tested within one mile of the Site exceeded the MCL for <br /> nitrate. <br /> Taking these factors into account, the actual nitrate loading experienced on the Site <br /> over time may be less than predicted. <br /> LOGE 2618 Page 13 <br />