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• CONCLUSIONS AND RECOMMENDATIONS In summary, the soil conditions examined near the proposed septic system drain field appear to be suitable. A satisfactory soil percolation rate of 1.6 minutes per inch was observed. The depth of ground water based on recent aquifer levels is approximately 93 to 105 feet below the ground surface, depending on the season. The ground-water flow direction is northeast at a rate of approximately five to six feet per mile in the vicinity of the Site. The on-site domestic water well was tested for nitrate and DBCP. Nitrate was detected at a concentration of 14.8 mg/L-N in the water sample. DBCP was detected in the sample at a concentration of 0.05 µg/L. The US EPA has set the Maximum Contaminant Level (MCL) for nitrate at 10 mg/L-N and the MCL for DBCP at 0.2 ppb (equivalent to µg/L). For health reasons, we recommend that the well water not be consumed until nitrate levels can be reduced to below the MCL. Utilizing bottled water for drinking may be a good option to consider. The San Joaquin County Environmental Health Department may be able to recommend other alternatives. Based on the current project, the use of on-site septic tanks and drain field systems on the Site is not expected to cause a buildup of nitrate in the aquifer above 5.09 mg/L-N. • This level falls below the US EPA drinking water recommendation of 10 mg/L-N. In fact, the actual impact to the aquifer will be much less since the nitrate loading equation is conservative and overestimates impacts. It should be noted, however, that based on the analytical results of the water sample from the domestic well, it appears nitrate levels in ground water beneath the Site already exceed the MCL. We believe the Site suitable for the use of a standard septic system utilizing leach lines and seepage pits. Based on the satisfactory result of the nitrate loading calculation, no nitrate mitigation is recommended. • LOGE 1628 Page 13