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CONCLUSIONS AND RECOMMENDATIONS In summary, the soil conditions examined near the proposed septic system drain fields were found to be suitable for septic systems. A satisfactory soil percolation rate of 6.9 min/in was observed in the shallow soil zone at the test location. The soil in the test location was found to be silty clay. The depth of ground water based on recent aquifer levels is approximately 85 to 90 feet below ground surface. Ground water flows to the north or northwest in the area at a rate of approximately 11 to 16 feet per mile. No wells are located on the Site, water is provided by a community well. No water sample was collected as part of this investigation. Based on the map reviewed, elevated nitrate levels are common for wells in the area. 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 15.0 mg/L, which exceeds the MCL of 10 mg/L-N. 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. The clay soil and deep ground water in the area may serve to limit the transportation of nitrate to the aquifer. Septic system construction should follow the San Joaquin County On -Site Wastewater Treatment Systems Standards (2017) where applicable. It is recommended that the new system utilize leach lines, leach lines with sumps, or a filter bed rather than deep seepage pits; this recommendation is intended to provide additional protection to ground water. 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 shallow leach field area to mitigate nitrate impacts; this option may be worth exploring for the Site. As an alternative if space is tight, a septic system engineered to reduce nitrate could be utilized with deep seepage pits. LOGE 2213 Page 14