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1444 MARIPOSA ROAD <br /> WKA No 2935 05 <br /> August 26, 1999 <br /> ' Page 15 <br /> A summary of the groundwater elevation data is included in Table 3 and shown on Plate No 3 <br /> A summary of analytical results for groundwater samples are included in Tables 4 and 5 Copies <br /> of the analytical reports and cham-of-custody documentation for our most recent phase of work <br /> ' are included in Appendix D Historic laboratory reports and chain-of-custody documents are <br /> included in various reports presented to San Joaquin County Public Health Services <br /> ' Conclusions and Recommendations <br /> The laboratory data obtained during our most recent field work appears to indicate that a very <br /> limited amount of contaminated soil remains beneath the site in the relative vicinity of the former <br /> ' excavation The perimeter of this soil contamination appears to extend outward to monitoring <br /> well MW 1 and borings B2, B3, and B5 and is present to a depth of approximately 82 feet It <br /> ' should be noted,however, that reported concentrations of TPH or BTEX at each of the soil <br /> boring Iocations was relatively low indicating that they are likely at or near the edge of the soil <br /> contamination <br /> Laboratory results for groundwater samples obtained from the three preexisting wells and the <br /> ' four new wells reveals that only trace concentrations of petroleum hydrocarbons appear to have <br /> migrated to the northwest and southeast The perimeter wells to the north and east report no <br /> detectable concentrations of TPH, BTEX and MTBE indicating that any groundwater <br /> contamination beneath the former tank pit has not spread to the north or east sides of the <br /> ' property <br /> One difficulty with sweeping conclusions with regard to contaminant concentrations in the three <br /> ' older wells (MW1 through MW3) is that the dramatically rising water levels have left the <br /> screened intervals in these wells far below the groundwater surface This poses a difficulty, <br /> ' because petroleum hydrocarbons reaching groundwater will for the most part remain at or near <br /> the water surface with very little dissolution <br /> diagrams reveals that screened intervals for MWl <br /> Review of the original well constructiongr � <br /> ' through MW3 extended from approximately 65 to 85 feet below surface grade Comparison with <br /> . historic groundwater elevation data reveals that the screened interval was submerged in these <br /> I ' � <br /> 1dbW <br /> ' WALLACE KUHL <br /> Recycled paper &ASSOCIATES INC <br />