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17 June 2003 <br /> AGE-NC Project No 95-0121 <br /> Page 4 of 5 <br />' Between February 1991 and May 1998, ground water elevations at the site generally <br /> increased from 26 feet to 7 feet below mean sea level(msl),however,between May 1998 and <br /> Present, ground water elevations have generally fluctuated between 7 feet and 11 feet below <br />' mean sea level (Table 2) <br /> • The ground water elevation at the site was generally between 7 and 16 feet above the <br />' screened intervals of wells MW-1 through MW-7, and probably yields samples more <br /> representative of deeper ground water conditions (Table 2) <br /> • The core of the dissolved petroleum hydrocarbon plume appears to be located In the area of <br />' wells MW-1 through MW-4 and MW-7 Analysis of ground water samples suggest the core <br /> of the plume is impacted by,TPH-g, TPH-d, BTEX and MTBE (Figures 4 and 5) <br />' The laboratory reported the TPH-d sample chromatograms from MW-1 through MW-4 and <br /> _ MW-7 to have significant gasoline range compounds (Appendix C) <br />' • BTEX and MTBE concentrations 1n ground water samples MW-1 through MW-4 and MW-7 <br /> were substantially above their respective Maximum Contaminant Levels In drinking water <br /> 5.0. RECOMMENDATIONS <br />' Based upon data collected during March 2003, AGE recommends <br />' • Continued semi-annual ground water monitoring at the site Semi-annual sampling events <br /> should be adequate to monitor ground water impacts at the site and should be re-evaluated <br /> on a semi-annual basis The next ground water monitoring event is tentatively scheduled for <br /> December 2003 , <br /> • A work plan addendum for cone penetrometer testing (CPT) is included with this report in <br /> Appendix A,data collected from CPT testingwill be utilized to(1)define the vertical extent <br /> Iof dissolved petroleum hydrocarbons, (2) better characterize the geological and hydro- <br /> geological framework underlying the mte, and (3) properly screen any additional deeper- <br /> screened ground water remediation wells (i a ground water extraction or ozone sparge) <br /> Upon SJCEHD review and approval of the work plan addendum, AGE will tentatively <br /> schedule field work <br /> I <br /> Advanced GeoEnvironmental,Inc <br /> f <br /> 4 <br />