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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. A satisfactory soil percolation rate of 10.0 min/in was observed in the shallow soil zone at the test location. The depth of ground water based on recent aquifer levels is approximately 78 to 80 feet below ground surface. Ground water flows down to the northeast at a rate of approximately 13 to 18 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 60 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 2.2 mg/L-N, well below the MCL of 10 mg/L-N. DBCP was detected at a concentration of 0.19 ug/L, just under the MCL of 0.2 ug/L. The MCL Goal for DBCP is zero. Based on a review of San Joaquin County Environmental Health Department maps of nitrate and DBCP detections in nearby wells, four wells within a half-mile radius of the subject Site have been tested. Nitrate was detected in three wells at concentrations between 0.1 and 5.0 mg/L-N, and in the fourth at a concentration between 5.1 and 10 mg/L-N. DBCP was detected in all four of the wells at concentrations over 0.2 ug/L. 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 6.2 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 with 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 1923 Page 12