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CONCLUSIONS AND RECOMMENDATIONS <br /> In summary, the soil conditions examined near the proposed septic disposal area for the <br /> new ADU on the Site were found to be suitable for a standard septic system. <br /> Satisfactory soil percolation rates of 22.7 min/in (shallow) and 2.03 min/in (deep) were <br /> observed at the test location. The soil in the test location was found to be sandy silt <br /> with clay to a depth of four feet, followed by sandy clay to seven feet, followed by clayey <br /> coarse sand to the full 7.64-foot depth of the hole. <br /> Based on maps of recent aquifer levels, the depth of ground water is approximately 180 <br /> to 208 feet below ground surface. Ground water appears to flow generally to the west <br /> in the area at a rate of approximately 6 to 14 feet per mile. <br /> A water sample was collected from the domestic well on the Site. Nitrate was detected <br /> in the water sample at a concentration of 2.0 mg/L-N, well below the MCL of 10 mg/L-N. <br /> DBCP was not detected in the water sample. <br /> Based on the methods and assumptions described, the nitrate loading calculation <br /> indicates that existing and proposed future on-site septic drain field systems on the Site <br /> have the potential to cause a buildup of nitrate in the aquifer up to 3.8 mg/L-N, well <br /> below the MCL of 10 mg/L-N. Because of the favorable result of the calculation, no <br /> nitrate mitigation is recommended at this time. <br /> Future septic system construction should follow the San Joaquin County On-Site <br /> Wastewater Treatment Systems Standards (2017) where applicable. In this area, most <br /> septic systems utilize leach lines with seepage pits. <br /> LOGE 2611 Page 14 <br />