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CONCLUSIONS AND RECOMMENDATIONS <br /> In summary, the project Site has been found suitable for the use of standard septic <br /> systems. <br /> Satisfactory soil percolation rates of 7.6 and 9.3 min/in were observed by Chesney <br /> Consulting in 2006 in the shallow soil zone at the location of the current septic system. <br /> The depth of ground water based on recent aquifer levels is approximately 103 to 125 <br /> feet below ground surface. The ground-water flow beneath the Site is to the north or <br /> northwest at a rate of approximately 16 to 20 feet per mile. Depth-to-water data were <br /> not available for the vicinity of the Site during the 1983 and 1999 high-water seasons. <br /> Because the percolation rates encountered fall between 5.0 and 30.0 min/in, the San <br /> Joaquin County Environmental Health Department will require an eight-foot separation <br /> from the bottom of the dispersal system to ground water. Based on the anticipated <br /> depth to water beneath the Site, this requirement should not necessitate any <br /> modification to standard systems. <br /> A water sample was collected from the domestic well on the Site as part of this <br /> investigation. Nitrate was detected in the sample at a concentration of 2.6 mg/L-N, <br /> below the MCL of 10 mg/L-N. DBCP was not detected in the sample; the MCL for <br /> DBCP is 0.2 ug/L. <br /> Based on the method and assumptions described, the nitrate loading calculation <br /> indicates that the use of on-site septic tanks and drain field systems on the Site have <br /> the potential to cause a buildup of nitrate in the aquifer up to 8.3 mg/L-N, below the US <br /> EPA drinking water recommendation of 10 mg/L-N. Based on the favorable result of the <br /> nitrate loading calculation, no nitrate mitigation is recommended. <br /> LOGE 20-19 Page 16 <br />