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CONCLUSIONS AND RECOMMENDATIONS In summary, the soil conditions examined near the proposed septic system drain field were found to be suitable for a standard septic system. A satisfactory soil percolation rate of 8.9 min/in was observed in the shallow soil zone at the test location. The soil in the test location was found to be silty sand. The depth of ground water based on recent aquifer levels is approximately 28 to 38 feet below ground surface. Ground water appears to flow to the northwest in the area; the ground-water gradient could not be calculated. A static water level of 38 feet below ground surface was reported on the domestic well permit. Because of the percolation rate between 5.0 and 30.0 min/in encountered in the test hole, the San Joaquin County Environmental Health Department will require an eight- foot separation from the bottom of the dispersal system to ground water. Based on the anticipated depth to ground water, no modifications to standard, shallow septic systems should be required. A water sample was collected from the domestic well on the Site as part of this investigation. Nitrate was detected in the sample at a concentration of 1.1 mg/L-N, well below the MCL of 10 mg/L-N. No DBCP was detected in the sample. Based on the methods and assumptions described, the nitrate loading calculation indicates that the use of on-site septic tanks and drain field systems on the Site has the potential to cause a buildup of nitrate in the aquifer up to 9.3 mg/L, below the MCL of 10 mg/L-N. Septic system construction utilizing leach lines, leach lines with shallow sumps, or a filter bed should follow the San Joaquin County On-Site Wastewater Treatment Systems Standards (2017) where applicable. Based on the results of the nitrate loading analysis, no nitrate mitigation is recommended. LOGE 20-25 Page 13