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CONCLUSIONS AND RECOMMENDATIONS In summary, the soil conditions examined near the location of the septic system drain field appear to be suitable. A satisfactory soil percolation rate of 0.97 minutes per inch was observed. The depth of ground water based on recent aquifer levels is relatively deep and approximately 100 to 112 feet below the ground surface. The ground-water flow direction is to the north or north-northeast at a rate of approximately 10 feet per mile. The on-site domestic water well was tested for nitrate and DBCP. Nitrate was detected at a concentration of 12.2 mg/L-NO3 in the water sample. DBCP was detected in the sample at a concentration of 1.93 µg/L. The US EPA has set the Maximum Contaminant Level (MCL) for nitrate as NO3 at 45 mg/L and the MCL for DBCP at 0.2 ppb (equivalent to µg/L). Because of the level of DBCP detected, we would recommend that the occupants of the Site consume bottled water until such time as the concentration can be reduce a ow a se of point-source water filters or deepening of the domestic well could potentially improve the water quality. The San Joaquin County Environmental Health Department may be able to provide additional suggestions. Based on the current project, the use of on-site septic tanks and drain Feld systems on the Site is not expected to cause a buildup of nitrate in the aquifer above 9.24 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. We believe the Site suitable for development with the use of standard septic systems. 1; We do not anticipate that the ground water quality will be negatively impacted, and no nitrate mitigation is recommended. LOGE 1122 Page 14