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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 standard septic system utilizing leach lines and seepage pits. Satisfactory soil percolation rates of 50.0 min/in and 4.55 min/in were observed in the shallow and deep soil zones. The soil in the test location was found to be clay to approximately 6.5 feet below ground surface, followed by silt with very fine sand and clay to 8 feet, followed by fine sand with silt to 8.14 feet. The depth of ground water based on recent aquifer levels is approximately 85 to 89 feet below ground surface. The ground-water flow is to the east at a rate of approximately 8 to 12 feet per mile in the vicinity of the Site. Because of the percolation rate between 1.0 and 5.0 min/in encountered in the deep test hole, the San Joaquin County Environmental Health Department will require a 20- foot separation from the bottom of the dispersal system to ground water. Based on the anticipated depth to ground water, no modifications to standard septic systems should be required. 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 2.9 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 regional maps of nitrate and DBCP detections reviewed, neither constituent appears to be a significant problem for wells in the area. Based on the methods and assumptions described, the nitrate loading calculation indicates that the use of on-site septic tanks and drain field systems on the Site has the potential to cause a buildup of nitrate in the aquifer up to 7.8 mg/L, below the maximum drinking water standard. As a result, no nitrate mitigation is recommended for the new septic system. LOGE 20-40 Page 14