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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 2.45 min/in was observed in the shallow soil zone at the test location. The soil at the test location was found to be sandy silt. The depth of ground water based on recent aquifer levels is approximately 83 to 89 feet below ground surface. Ground water flows down to the southeast at a rate of approximately 6 to 10 feet per mile. Because of the percolation rate between 1.0 and 5.0 min/in encountered in the test hole, the San Joaquin County Environmental Health Department will require a 20 -foot separation from the bottom of the dispersal system to ground water, unless mitigated by system design or enhancement. Given the estimated depth to water, no modification to a standard system should be necessary to fulfill this requirement No water sample was collected as part of this investigation; the well is not currently connected to a power supply. Based on maps reviewed, neither nitrate nor DBCP appear to be a concern in the immediate vicinity of the Site, though DBCP is a widespread problem in the eastern Lodi area. According to records reviewed, an old house with two wells and a septic system was present on the Site in 1996; the existing well on the Site appears to be the agricultural well. Two underground gasoline storage tanks were removed from the Site in 1997 under the oversight of San Joaquin County Public Health Services. This report is not intended to be an assessment of contamination sources, and no further investigation of the house area or former tanks was conducted. Based on the methods and assumptions described, 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 1.3 mg/L-N. This level falls well 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 2221 Page 14