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CONCLUSIONS AND RECOMMENDATIONS In summary, the soil conditions examined near the existing septic system drain field were found to be suitable. A satisfactory soil percolation rate of 2.8 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 80 feet below the ground surface. The ground-water flow direction is predominantly toward the northeast at a rate of approximately 12 to 18 feet per mile in the vicinity of the Site. 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 3.6 mg/L-N, well below the MCL of 10 mg/L-N. DBCP was detected at a concentration of 0.18 ;AWL, slightly below the MCL of 0.2 Ag/L. The US EPA has set the MCL for DBCP at 0.2 kig/L because it believes that, given present technology and resources, this is the lowest level to which water systems can reasonably be required to remove this contaminant should it occur in drinking water. The Maximum Contaminant Level Goal (MCLG) for DBCP is zero. Because the percolation rate encountered falls between 1.0 and 5.0 min/in, the San Joaquin County Environmental Health Department will require a 20-foot separation from the bottom of the dispersal system to ground water. Based on the predicted depth to ground water of approximately 80 feet, no modifications to standard septic systems should be required. 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 8.5 to 8.8 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. LOGE 1906 Page 17