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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 septic system. A satisfactory soil percolation rate of 7.57 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 115 to 145 feet below ground surface. The ground-water flow beneath the Site is to the north or northwest at a rate of approximately 18 to 21 feet per mile. Depth-to-water data were not available for the vicinity of the Site during the 1983 and 1999 high-water seasons. Because the percolation rate encountered falls between 5.0 and 30.0 min/in, 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 water beneath the Site, this requirement should not present a difficulty. 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 9.9 mg/L-N, just below above the MCL of 10 mg/L-N. DBCP was not detected in the sample; the MCL for DBCP is 0.2 [g/L. Based on a review of San Joaquin County Environmental Health Department maps of nitrate and DBCP detections in nearby wells, it appears that four wells within a half-mile radius of the subject Site have been tested for nitrate; it was detected in one at a concentration between 5.1 and 10.0 mg/L-N, and in the other three at a concentration greater than 10.0 mg/L-N. Two wells within one-half mile of the Site were tested for DBCP; no DBCP was detected in either well. Based on the method and assumptions described, the nitrate loading calculation indicates that the use of on-site septic tanks and drain field systems on the Site have the potential to cause a buildup of nitrate in the aquifer of 15.2 mg/L-N, above the US EPA drinking water recommendation of 10 mg/L-N. However, based on the conservative nature of the calculation, depth-#o-water beneath the Site, and clay soil present in the area, it is the professional opinion of Live Oak that shallow septic effluent from the subject Site is unlikely to contribute significantly to a build=up of nitrate in the ground water. Use of a standard, shallow septic system should be permitted for the new home. It is recommended that the new standard system utilize only leach lines or a filter bed rather than deep seepage pits; this recommendation is intended to provide additional protection to ground water, since the nitrate loading result exceeded the MCL, and some nearby wells show elevated levels of nitrate. As an alternative if space is tight, a septic system engineered to reduce nitrate could be utilized with deep seepage pits. LOGE 1914 Page 13