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CONCLUSIONS AND RECOMMENDATIONS In summary, the soil conditions examined near the proposed septic disposal field of the Site were found to be suitable for a septic system utilizing leach lines or a filter bed. A satisfactory soil percolation rate of 2.1 min/in was observed at the test location. The soils in the test location were found to be silty, very fine sand. The depth of ground water based on recent aquifer levels is approximately 23 to 25 feet below ground surface. The ground -water flow is to the northeast in the general area, at a rate of approximately 3 to 4 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, only shallow septic systems (leach lines or filter beds) should be constructed at this location. 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 1.6 mg/L-N, well below the MCL of 10 mg/L-N. DBCP was not detected in the sample. Based on the methods and assumptions described, the nitrate loading calculation indicates that the use of existing and proposed septic tanks and drain field systems on the Site has the potential to cause a buildup of nitrate in the aquifer up to 12.1 mg/L-N, slightly over the maximum drinking water standard of 10 mg/L-N. It should be remembered that the Hantzsche and Finnemore equation is a conservative method for determining potential impacts, and actual nitrate loading experienced on the Site over time may be less than predicted. Additionally, as discussed above, current nitrate levels at the Site are well below the MCL, despite existing residential development. Although Live Oak cannot make engineering recommendations, we are aware that the San Joaquin County Environmental Health Department often allows the use of standard systems with oversized septic tanks in cases where a 30 percent reduction would bring the nitrate loading under the MCL; the subject Site's nitrate loading result meets this criterion. The use of a shallow septic leach field rather than deeper sumps is anticipated to provide additional reduction in nitrate loading. LOGE 2237 Page 14