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CONCLUSIONS AND RECOMMENDATIONS <br /> In summary, the soil conditions examined near the existing septic system drain fields <br /> were found to be suitable. Satisfactory soil percolation rates of 7.81 min/in (northern <br /> parcel) and 31.25 min/in (southern parcel) were observed in the shallow soil zones at <br /> the test locations. <br /> Because of the percolation rate between 5.0 and 30.0 min/in encountered in the <br /> northern test hole, the San Joaquin County Environmental Health Department will <br /> require an eight-foot separation from the bottom of the dispersal system to ground <br /> water; this requirement would affect any future construction. Similarly, a standard five- <br /> foot separation would be required for the southern parcel based on the percolation rate <br /> encountered between 30.0 and 120 min/in. <br /> The depth of ground water based on recent aquifer levels is extrapolated from the <br /> available maps to be 10 to 20 feet below ground surface. The ground-water flow <br /> direction and gradient could not be calculated. San Joaquin County experienced its <br /> highest recent ground-water levels in 1983 and 1999. Review of ground-water maps for <br /> these years reveals that depth to water would have been approximately 10 feet in 1999; <br /> the Thornton area was not mapped in 1983. <br /> No wells are located on the Site; the residences receive municipal water. No water <br /> sample was collected for this study. <br /> Based on a review of San Joaquin County Environmental Health Department maps of <br /> nitrate and DBCP detections in nearby wells, it appears that only one well within one- <br /> half mile of the Site has been tested for nitrate and DBCP; neither constituent was <br /> detected. <br /> The soils within the proposed sewage disposal areas of the Site have demonstrated <br /> satisfactory percolation rates for the use of shallow septic systems in accordance with <br /> the requirements of the San Joaquin County Environmental Health Department. Septic <br /> system construction utilizing leach lines or a filter bed should follow the San Joaquin <br /> County On-Site Wastewater Treatment Systems Standards (2017) where applicable. <br /> LOGE 1926a Page 8 <br />