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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 a standard, shallow septic system utilizing leach lines or a filter bed. A satisfactory soil percolation rate of 5.2 min/in was observed in the shallow soil zone at the test location. The depth of ground water based on recent aquifer levels is estimated to be 35 to 40 feet below ground surface. The ground-water flow beneath the Site is to the north at a rate of three to six feet per mile. San Joaquin County experienced its highest recent ground-water leVelg. in 1983 and 1999; depth to water beneath the Site was approximately 2o feet during spring of these years. Because the "percor(tio-n rate encountered falls between 5.0 and 30 -mm/in, the San Joaquin County Environmental Health Department will require an eight-foot,separation from the bottom of the dispersal system to ground water, or mitigation by,system design or enhancement. Based on the predicted depth to water, no modification to standard, shallow systems should be required. A water sample was collected from the domestic well on the Site a -part of thi investigation. Nitrate was detected in the sample at a concentratiOn 17.1_mg/L-N slightly above the MCL of 10 mg/L-N. DBCP was not detected in the sa ple; the M L for DBCP is 0.2 p.g/L. It is recommended for health reasons 1h-it bottled water be consumed until the concentration of nitrate can be reduced to below the MCL. The San Joaquin County Environmental Health Department may have recommendations for filtration systems to reduce nitrate levels in the drinking water. Based on a review of the San Joaquin County Environmental Health Department's map of nitrate detections in nearby wells, six wells within a half-mile radius of the subject Site have been tested. Nitrate was detected in two of the wells at concentrations between 5.1 and 10 mg/L-N, and in the remaining four at concentrations over 10 mg/L-N. Three wells within a half-mile radius of the Site were tested for DBCP; no DBCP was detected. The surrounding agricultural properties are mainly orchards; elevated nitrate levels in the area likely derive from fertilizer application on these properties. 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 4.4 mg/L-N. This level falls below the US EPA drinking water recommendation of 10 mg/L-N. Because of the satisfactory result of the nitrate loading calculation, no nitrate mitigation is recommended. LOGE 1924 Page 12