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CONCLUSIONS AND RECOMMENDATIONS In summary, the soil conditions examined near the existing septic system drain fields were found to be suitable for standard, shallow septic systems utilizing leach lines, leach lines with sumps, or filter beds. Satisfactory soil percolation rates of 5.56 min/in (Parcel 1) and 4.17 min/in (Parcel 2) were observed at the test locations. The soils in the test locations were found to be silty sand with clay (Parcel 1) and silty sand (Parcel 2). The percolation tests are considered representative of an area approximately 100 feet in radius. The depth of ground water based on recent aquifer levels is approximately 43 to 51 feet below ground surface. The ground-water flow is to the northwest at a rate of approximately 5 feet per mile in the vicinity of the Site. Water samples were collected from the both domestic wells on the Site as part of this investigation. Nitrate was detected in the sample from the southern well at a concentration of 9.6 mg/L-N, below the MCL of 10 mg/L-N. DBCP was detected at a concentration of 0.02 ug/L, below the MCL of 0.2 ug/L. In the sample from the northern well, nitrate was detected at 18.9 mg/L-N (above the MCL), and DBCP was detected at 0.01 ug/L (below the MCL). It is recommended that the residents at the northern house consume bottled water until the nitrate level can be brought down below the MCL. The San Joaquin County Environmental Health Department should be contacted for recommendations about water filtration. 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 for Parcel 1 and 1.5 mg/L-N for Parcel 2; both results are below the maximum drinking water standard of 10 mg/L-N. Because of the favorable results of the nitrate loading calculations, no nitrate mitigation is recommended at this time. LOGE 2111 Page 15