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13 February 2003 <br /> AGE-NC Project No 99-0624 <br /> 1 Page 4of5 <br /> from MW-1 and MW-3 Toluene was not detected in any water samples Benzene <br /> 1 concentrations were above the DHS's Maximum Contaminant Level (MCL) of 1 0,ugh in <br /> drinking water <br /> 10 Utilizing EPA Method 8260B, MTBE was detected from wells MW-1, MW-2 and MW-3 <br /> at concentrations as lugh as 17,000,ugll(MW-2) The MTBE concentrations were above the <br /> Primary MCL of 13 ,ugll in drinking water <br /> 10 The elevated concentrations of petroleum hydrocarbons detected in samples collected from <br /> well MW-2 Indicate that this well is within or near the dissolved petroleum hydrocarbon <br /> "core area" of the plume (Figure 4) During ten consecutive quarterly ground water <br /> 1 monitoring events, the TPH-g concentrations in well MW-2 have generally fluctuated at <br /> between 140µg/1 and 8,900,ug/1, and MTBE concentrations have fluctuated significantly at <br /> between 130µg11 and 17,000µg/1 <br /> 10 The significant fluctuations in MTBE-impacted groundwater,combined with the laboratory <br /> notations that all chromatograms from MW-2 ground water samples have contained <br /> 1 significant, unmodified or weakly modified gasoline, could be Interpreted as indications of <br /> a relatively new release <br /> • <br /> I <br /> 5.0. RECOMMENDATIONS <br /> IBased upon data collected during November 2002, AGE recommends <br />' a Continued quarterly ground water monitoring and sampling, the next quarterly monitoring <br /> event Is scheduled for February 2003 <br /> • Performance of a receptor survey to locate potential receptors within 2,000 feet of the site <br />' 0 Preparation of a feasibility studies report to evaluate soil and ground water remediation <br /> alternatives at the site <br /> In response to an 08 August 2002 verbal directive from the SJCEHD, AGE submitted a work plan <br /> addendum, dated 03 September 2002, to further assess the vertical extent of petroleum-impacted <br /> 1 ground water in the area near MW-2, and the lateral extent of impacted ground water south- <br /> southwest of well MW-2 and east-northeast of the fuel dispensing area Upon work plan approval <br />' by the SJCEHD, AGE will submit a pre-approval package to the UST Cleanup fund and schedule <br /> field work <br />' 6.0. LIMITATIONS <br />' Advanced GeoEnvironmental,Inc <br /> I <br />