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CONCLUSIONS AND RECOMMENDATIONS <br /> In summary, the soil conditions examined near the existing septic system drain field <br /> were found to be suitable for a standard, shallow septic system utilizing leach lines or a <br /> filter bed. <br /> A satisfactory soil percolation rate of 20.8 min/in was observed in the shallow soil zone <br /> at the test location. The soil in the test location was found to be silty clay and silty clay <br /> with sand. <br /> Based on well drilling records and maps reviewed, ground water is anticipated to be <br /> encountered approximately 20 to 25 feet below ground surface at the Site. The ground- <br /> water gradient and flow direction could not be determined. <br /> Because of the percolation rate between 5.0 and 30.0 min/in encountered in the test <br /> hole, the San Joaquin County Environmental Health Department will require an eight- <br /> foot separation from the bottom of the dispersal system to ground water. Based on the <br /> anticipated depth to ground water, no modifications to standard, shallow septic systems <br /> should be required. No new construction is anticipated. <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 2.6 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 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 3.4 mg/L, well below the MCL <br /> of 10 mg/L-N. No nitrate mitigation is recommended. <br /> LOGE 20-15 Page 14 <br />