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CONCLUSIONS AND RECOMMENDATIONS <br />In summary, the soil conditions examined near the proposed septic system drain field <br />were found to be suitable for a standard septic system utilizing leach lines and seepage <br />pits. <br />A satisfactory soil percolation rate of 10.0 min/in was observed in the deep soil zone at <br />the test location. The soils in the test location were found to include strata of clay, silt, <br />and sand. The percolation test is considered representative of soils within a 100-foot <br />radius of the test location. <br />Based on maps reviewed, ground water is anticipated to be encountered approximately <br />85 to 90 feet below ground surface at the Site. The ground-water gradient beneath the <br />Site is to the east at a rate of approximately 6 to 15 feet per mile. <br />Because of the percolation rate between 5.0 and 30.0 min/in encountered in the deep <br />test hole, the San Joaquin County Environmental Health Department will require an <br />eight-foot separation from the bottom of the dispersal system to ground water. Based <br />on the anticipated depth to ground water, no modifications to standard septic systems <br />should be required. <br />A water sample was collected from the domestic well on the Site. Nitrate was detected <br />at a concentration of 5.8 mg/L-N, well below the MCL of 10 mg/L-N. DBCP was not <br />detected in the sample. Neither nitrate nor DBCP appears to be a significant problem in <br />nearby wells, according to water testing maps reviewed. <br />Based on the methods and assumptions described, the nitrate loading calculation <br />indicates that the use of on-site septic tanks and drain field systems on the Site has the <br />potential to cause a buildup of nitrate in the aquifer up to 4.7 mg/L, well below the MCL <br />of 10 mg/L-N. As a result, no nitrate mitigation is recommended at this time. <br />LOGE 20-59 Page 14