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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 27.8 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 82 to 85 feet below ground surface. The ground-water flow is to the east or southeast at a rate of four to seven feet per mile. The highest recent ground-water levels for San Joaquin County were experienced in 1983 and 1999; depth to ground water was approximately 58 to 62 feet for these years. Because of the percolation rate between 5.0 and 30.0 min/in encountered in the test hole, 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 the anticipated depth to ground water, no modifications to standard septic 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 5.3 mg/L-N, below the MCL of 10 mg/L-N. DBCP was not detected in the sample; the MCL for DBCP is 0.2 ug/L. 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 Site have been tested for nitrate. One of these wells was found to contain nitrate at a concentration between 0.1 and 5.0 mg/L, three were found to contain nitrate at a concentration between 5.1 and 10 mg/L-N, and one was found to contain nitrate at a concentration over 10 mg/L-N; no nitrate was detected in the sixth well. Based on review of the DBCP map, two wells within a half-mile radius of the Site have been tested for DBCP; no DBCP was detected in either well. Based on the methods and assumptions described, the nitrate loading calculation indicates that the use of on-site septic tanks and drain field systems on the Site has the potential to cause a buildup of nitrate in the aquifer up to 11.0 mg/L. However, because of the conservative nature of the calculation, the actual impact to ground water may be considerably less. Based on the significant depth to water, clayey soil present, and lack of existing nitrate exceedance in all but one nearby well, it is the professional opinion of Live Oak that effluent from a second septic system on the subject Site is unlikely to contribute to a problematic build-up of nitrate in the ground water. A standard system is recommended. LOGE 20-03 Page 15