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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 standard septic systems utilizing leach lines and seepage pits. A satisfactory soil percolation rate of 12.5 min/in was observed in the deep soil zone at the test location. No movement of water was observed in the shallow soil zone. The depth of ground water based on recent aquifer levels is approximately 120 to 127 feet below ground surface. The ground-water flow is to the south or southeast at a rate of 4 to 10 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 100 to 120 feet for these years. 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 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 1.6 mg/L-N, well below the MCL of 10 mg/L-N. No DBCP was detected in the sample. Based on a review of the San Joaquin County Environmental Health Department's maps of nitrate and DBCP detections in nearby wells, neither contaminant appears to be present above the MCL in the vicinity of the Site. Three dairies are located within a third of a mile of the Site; however, as presented on the nitrate map reviewed, the dairies do not appear to have caused an elevation of nitrate levels in the area above the MCL. Utilizing 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 4.5 mg/L, well below the MCL of 10 mg/L-N. Based on the very slow percolation in the shallow soil zone and the history of septic system repairs on the Site, Live Oak recommends installing standard septic systems that are as large as is practical and ensuring that they are well maintained over time. Please contact our office if further information is desired. Because of the favorable result of the nitrate loading study, no nitrate mitigation is recommended. LOGE 20-20 Page 15