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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 3.8 min/in was observed in the shallow soil zone at the test location. The soil in the test location was found to be sandy clay, clay, and clayey sand. The depth of ground water based on recent aquifer levels is approximately 55 to 61 feet below ground surface. The ground-water flow is to the northeast in the area at a rate of 5 to 7 feet per mile. The highest recent ground-water levels for San Joaquin County were experienced in 1983 and 1999; depth to ground water was approximately 50 to 63 feet for these years. Because of the percolation rate between 1.0 and 5.0 min/in encountered in the test hole, the San Joaquin County Environmental Health Department will require a 20-foot separation from the bottom of the dispersal system to ground water. Based on the anticipated depth to ground water, no modifications to standard 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 0.2 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 3.8 mg/L-N, well below the MCL of 10 mg/L-N. Septic system construction utilizing leach lines and seepage pits 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 20-24 Page 15