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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 system utilizing leach lines or a filter bed. A satisfactory soil percolation rate of 10.0 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 19 to 25 feet below ground surface. The ground-water flow beneath the Site is to the northwest at a rate of approximately seven to ten 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 11.7 mg/L-N, slightly above the MCL of 10 mg/L-N. DBCP was not detected in the sample; the MCL for DBCP is 0.2 ug/L. It is recommended for health reasons that bottled water be consumed until the concentration of nitrate can be reduced to below the MCL. The San Joaquin County Environmental Health Department may have recommendations for well deepening or filtration systems to reduce nitrate levels in the drinking water. Based on a review of San Joaquin County Environmental Health Department maps of nitrate and DBCP detections in nearby wells, it appears that two 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 at a concentration greater than 10.0 mg/L-N. One well within one-half mile of the Site was tested for DBCP; no DBCP was detected in the sample. Based on the method and assumptions described, 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 above the US EPA drinking water recommendation of 10 mg/L-N. The method utilized, as required by the San Joaquin County Environmental Health Department, is highly conservative and may overestimate nitrate impacts. Because of the result of the nitrate loading calculation, nitrate mitigation is recommended for the proposed new septic system. Based on current San Joaquin County Environmental Health Department policy, installation of an engineered septic system will most likely be required. LOGE 1911 Page 13