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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. A <br /> satisfactory soil percolation rate of 13.9 min/in was observed in the shallow soil zone at <br /> the test location. The soil in the test location was found to be sandy silt. <br /> Based on maps of recent aquifer levels, the depth of ground water is approximately 62 <br /> to 64 feet below ground surface. Ground water flows generally to the east in the area at <br /> a rate of approximately 5 to 10 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 6.1 mg/L-N, below the MCL of 10 mg/L-N. <br /> DBCP was detected at a concentration of 0.07 µg/L in the water sample, below the MCL <br /> of 0.2 µg/L but over the MCLG of zero. Although the DBCP result is below the MCL, the <br /> owner may wish to consider filtration systems to further reduce the concentration of this <br /> contaminant; because DBCP is a volatile chemical, a point-of-entry filtration system <br /> would be preferable to a single-faucet filter. <br /> Based on the methods and assumptions described, the nitrate loading calculation <br /> indicates that existing and proposed on-site septic drain field systems on the Site have <br /> the potential to cause a buildup of nitrate in the aquifer up to 9.4 mg/L-N, below the <br /> MCL of 10 mg/L-N. Because of the favorable result of the calculation, no nitrate <br /> 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 2605 Page 14 <br />