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CONCLUSIONS AND RECOMMENDATIONS In summary, the project Site has been found suitable for the use of standard septic systems utilizing leach lines, leach lines with sumps, leach lines with seepage pits, or filter beds. A satisfactory soil percolation rate of 5.56 min/in was observed in the shallow soil zone near the septic system replacement area. The soil in the test location was found to be sandy silt; the Web Soil Survey lists the area as Stomar clay loam. The depth of ground water based on recent aquifer levels is approximately 105 to 133 feet below ground surface. The ground-water flow beneath the Site is to the north or northwest at a rate of approximately 16 to 20 feet per mile. Because the percolation rates encountered fall 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 necessitate any modification to standard systems. The Site is the former location of Triple E Produce, which was investigated for pollution of the ground water with trihalomethanes (especially chloroform) from 1990 through 2005 under the oversight of the California Regional Water Quality Control Board. In 2005, the California Regional Water Quality Control Board issued a No Further Action letter based on the low and stable concentrations of chloroform detected. A second case, in which Triple E is listed as a land disposal site, remains open at the California Regional Water Quality Control Board; no information was available for this case. A water sample was collected from the well on the Site as part of this investigation. Nitrate was detected in the sample at a concentration of 3.2 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 the map reviewed, nitrate levels do exceed the MCL at other wells in the vicinity. 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 up to 9.4 mg/L-N, below the US EPA drinking water recommendation of 10 mg/L-N. Because of the favorable result of the nitrate loading analysis, no nitrate mitigation is recommended art this time. LOGE 20-60 Page 15