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CONCLUSIONS AND RECOMMENDATIONS <br />In summary, the soil conditions examined near the proposed septic system drain field <br />were found to be suitable for standard septic systems utilizing leach lines and seepage <br />pits. A satisfactory soil percolation rate of 12.5 min/in was observed in the shallow soil <br />zone at the test location. <br />The depth of ground water based on recent aquifer levels is approximately 118 to 129 <br />feet below ground surface. The ground -water flow is to the southeast at a rate of <br />approximately six feet per mile. <br />A water sample was collected from the domestic well on the Site as part of this <br />investigation. Nitrate was detected in the sample at a concentration of 1.6 mg/L-N, well <br />below the MCL of 10 mg/L-N. No DBCP was detected in the sample. <br />Based on a review of the San Joaquin County Environmental Health Department's <br />maps of nitrate and DBCP detections in nearby wells, neither contaminant appears to <br />be present above the MCL in the vicinity of the Site. <br />Utilizing the methods and assumptions described, the nitrate loading calculation <br />indicates that the use of on-site septic tanks and drain field systems on the Site has the <br />potential to cause a buildup of nitrate in the aquifer up to 6.3 mg/L, well below the MCL <br />of 10 mg/L-N. <br />Because of the favorable result of the nitrate loading calculation, no nitrate mitigation is <br />recommended at this time. <br />LOGE 2203 Page 14 <br />