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CONCLUSIONS AND RECOMMENDATIONS In summary, the soil conditions in the percolation test locations appear to be suitable for use with on-site septic systems. Satisfactory soil percolation rates of 9 and 31 min/in were observed by Neil O. Anderson & Associates in the test locations. The depth of ground water based on recent aquifer levels is estimated to range between 19 to 28 feet below ground surface. Based on maps reviewed, the ground-water flow is to the southeast at a rate of approximately four to six feet per mile. Because of the percolation rate encountered between 5 and 30 min/in at location P1, the San Joaquin County Environmental Health Department will require an eight-foot separation from the bottom of the dispersal system to ground water. Based on the anticipated depth to ground water beneath the Site, no modifications to standard shallow septic systems should be required. According to the San Joaquin County Environmental Health Department nitrate map reviewed, three wells within a one-mile radius of the subject Site have been tested for nitrate. Nitrate was detected in two wells at concentrations between 5.1 and 10.0 mg/L- N, and in the third at a concentration over 10.0 mg/L (this data point may represent the water sample collected on the Site, discussed above). According to the DBCP map, one well within the same area was tested; DBCP was not detected in the well. The presence of elevated levels of nitrate in the ground water may be attributable to the Lima Dairy, located approximately 900 feet east and southeast of the Site. This facility has impacted ground water with nitrate and ammonia from its wastewater pond and unlined wastewater channels. The White Slough Water Pollution Control Plant, located approximately one-half mile south of the Site, may also have contributed to nitrate levels in the area. The on-site domestic water well was tested for nitrate and DBCP in 2019. Nitrate was detected at a concentration of 36.8 mg/L-N in the water sample, above the US EPA drinking water recommendation of 10 mg/L-N. DBCP was not detected in the sample. 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 water may be a good alternative to consider. Based on the results of the percolation testing, we believe the Site suitable for the use of standard septic systems utilizing leach lines or filter beds. LOGE 20-02 Page 9