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CONCLUSIONS AND RECOMMENDATIONS <br />In summary, the soil conditions examined near the potential future septic disposal field <br />on the Site were found to be suitable for standard septic systems utilizing leach lines <br />and seepage pits. <br />A satisfactory soil percolation rate of 3.1 min/in was observed at the test location. The <br />soil in the test location was found to be sandy silt. <br />The depth of ground water based on recent aquifer levels is approximately 67 to 68 feet <br />below ground surface. Ground water appears to flow to the east in the vicinity of the <br />Site, at a rate of approximately seven feet per mile. <br />Because of the percolation rate between 1.0 and 5.0 min/in encountered in the test <br />hole, the San Joaquin County Environmental Health Department will require a 20 -foot <br />separation from the bottom of the dispersal system to ground water, unless mitigated by <br />system design or enhancement. Given the estimated depth to water, no modifications <br />to standard septic systems will be required. <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 1.4 mg/L-N, well <br />below the MCL of 10 mg/L-N. DBCP was not detected in the sample. <br />Based on the methods and assumptions described, the nitrate loading calculation <br />indicates that the use of the existing septic system, combined with maximum future <br />trucking use on the Site, have the potential to cause a buildup of nitrate in the aquifer up <br />to 3.6 mg/L-N, well below the maximum drinking water standard of 10 mg/L-N. Because <br />of the favorable result, no nitrate mitigation is recommended at this time. <br />LOGE 2236 Page 14 <br />