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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. A satisfactory soil percolation rate of 5.1 min/in was <br />observed in the shallow soil zone at the test location. The soil at the test location was <br />found to be sandy silt. <br />The depth of ground water based on recent aquifer levels is approximately 81 to 89 feet <br />below ground surface. Ground water flows down to the northeast at a rate of <br />approximately 12 feet per mile. <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 6.7 mg/L-N, <br />below the MCL of 10 mg/L-N. DBCP was detected at a concentration of 0.81 µg/L, <br />substantially over the MCL of 0.2 µg/L. It is recommended that occupants of the Site <br />consume bottled water until such time as the level of DBCP can be brought below the <br />MCL. The San Joaquin County Environmental Health Department should be contacted <br />to discuss long-term recommendations, such as point -of -entry water filtration or well <br />deepening. <br />Based on the methods and assumptions described, the use of on-site septic tanks and <br />drain field systems on the Site is not expected to cause a buildup of nitrate in the aquifer <br />above 6.5 mg/L-N. This level falls below the US EPA drinking water recommendation of <br />10 mg/L-N. It should be noted that, as discussed above, the current nitrate level in the <br />domestic well was found to be 6.7 mg/L-N. <br />We believe the Site suitable for the use of standard septic systems with leach lines and <br />seepage pits. Based on the satisfactory result of the nitrate loading calculation, no <br />nitrate mitigation is recommended for the current project. <br />LOGE 2212 Page 13 <br />