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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 4.39 min/in was observed in the shallow soil zone at the test location. The soil in the test location was found to be sandy silt and silty sand. The depth of ground water based on recent aquifer levels is approximately 15 to 18 feet below ground surface. The ground-water flow is to the northeast at a rate of approximately 2 to 3 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 5.6 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 13.9 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. It is also worth noting that the Site is located in a rural/agricultural area with few neighbors, so that the cumulative impact of development will be substantially less than in a more densely populated area. 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. Recent San Joaquin County Environmental Health Department policy has been to evaluate each project on a case-by-case basis to determine whether nitrate mitigation is warranted. Although Live Oak cannot make engineering recommendations, we are aware that in the past the San Joaquin County Environmental Health Department has allowed the use of an oversized septic tank combined with soil amendments in the leach field area to mitigate nitrate impacts; this option may be worth exploring for the Site. LOGE 2109 Page 13