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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 septic system. A satisfactory soil percolation rate of 1.3 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 17 to 24 feet below ground surface. The ground-water flow is to the north at a rate of approximately 3 to 4 feet per mile. 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, unless mitigated by system design or enhancement. 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 5.4 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 16.4 mg/L. It should be remembered that the Hantzsche and Finnemore equation is a conservative method for determining potential impacts, and actual nitrate loading experienced on the Site over time may be less than predicted. Septic system construction utilizing leach lines 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, a nitrate-mitigating septic system will most likely be required for the new development by the San Joaquin County Environmental Health Department. LOGE 20-26 Page 13