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CONCLUSIONS AND RECOMMENDATIONS In summary, the soil conditions near the proposed septic system drain field were found to be suitable. Satisfactory soil percolation rates of 40 min/in (shallow) and 8.6 min/in (deep) were obtained by Armstrong Engineering & Development, LTD in the percolation test location. The depth of ground water based on recent aquifer levels is approximately 80 to 90 feet below ground surface. Ground water flows down to the east-northeast at a rate of approximately eight to 13 feet per mile. The highest recent ground-water levels for the area were experienced in spring of 1983 and 1999; at these times, ground water would have been present at approximately 65 to 75 feet below ground surface. Because the percolation rate encountered falls between 5.0 and 30 min/in, 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 depth to water in the area, no modifications to standard 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 5.2 mg/L-N, well below the MCL of 10 mg/L-N. DBCP was not detected in the sample. Based on a review of the San Joaquin County Environmental Health Department map of nitrate detections in nearby wells, 11 wells within a half-mile radius of the subject Site have been tested for nitrate. Nitrate was detected in seven of these wells at concentrations between 0.1 and 5.0 mg/L-N, and in three at concentrations between 5.1 and 10 mg/L-N. No nitrate was detected in the final well. According to the map of DBCP detections, seven wells within a half-mile radius of the Site have been tested for DBCP. DBCP was detected in one of the wells at a concentration between 0.01 and 0.2 ug/L; no DBCP was detected in the other six wells. Based on the current project, the use of on-site septic tanks and drain field systems on the Site is not expected to cause a buildup of nitrate in the aquifer above 6.7 mg/L-N. This level falls below the US EPA drinking water recommendation of 10 mg/L-N. We believe the Site suitable for the use of standard septic systems utilizing leach lines and seepage pits. Based on the satisfactory result of the nitrate loading calculation, no nitrate mitigation is recommended for the current project. LOGE 1931 Page 13