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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 septic system utilizing leach lines or a filter bed. A satisfactory soil percolation rate of 4.6 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 13 to 16 �� feet below ground surface. The ground-water flow beneath the Site is to the north or southwest; the rate could not be calculated. San Joaquin County experienced its highest recent ground-water levels in 1983 and 1999. The Site is outside the mapped area for 1983; depth to water beneath the Site was approximately 10 feet in 1999. 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, or mitigation by system design or enhancement. The San Joaquin County Environmental Health Department may require installation of a shallow/modified septic system to mitigate the shallow depth to water. No wells are currently located on the Site; no water sample was collected as part of this study. Based on a review of the San Joaquin County Environmental Health Department map of nitrate detections in nearby wells, six wells within a one-mile radius have been tested for nitrate; it was detected in all six at a concentration greater than 10.0 mg/L-N. The elevated nitrate detections most likely result from seven large dairies located in the area; many of the samples appear to have been collected at the dairies. One well within a one-mile radius of the Site was tested for DBCP; no DBCP was detected. The Maximum Contaminant Level (MCL) set by the US EPA for nitrate is 10 mg/L-N; the MCL for DBCP is 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 4.6 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 1914 Page 11