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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 proposed development on the Site may cause a buildup of <br /> nitrates in the aquifer above 10 mg/L-N. <br /> There are three mitigating factors that should be considered, however, when evaluating <br /> this Site's impact to ground water: <br /> • The Hantzsche and Finnemore equation is a conservative method for <br /> determining potential impacts, and actual nitrate loading experienced on the Site <br /> over time may be less than predicted. 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. In addition, 2020 was a particularly dry year; <br /> because data from only four years are considered by the required method, undue <br /> weight is placed on the 2020 rainfall values. <br /> • Based on the clayey soil type present on the Site, it is likely that adsorption of <br /> nitrate ions to clay will occur as percolating effluent travels downward through the <br /> vadose zone. The soil factors included in the equation may not reflect the full <br /> extent of nitrate reduction experienced. <br /> • According to the San Joaquin County Environmental Health Department's map of <br /> nitrate detections, none of the four wells tested within a one-mile radius of the <br /> Site currently exceed the MCL for nitrate. <br /> For protection of the ground water, it is recommended that only shallow septic systems <br /> utilizing leach lines or filter beds be installed on the Site. Recent San Joaquin County <br /> Environmental Health Department policy has been to evaluate each project on a case- <br /> by-case basis to determine whether additional measures to mitigate nitrate should be <br /> employed. <br /> LOGE 2106 Page 13 <br />