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I <br /> 13 August 1997 <br /> AGE-NC Project No 95-0130 <br /> IPage 4 of 5 <br /> VW-3A <br /> • MTBE was detected in samples collected from wells MW-2, MW-3, VW-i C, VW-2A and <br /> VW-3A If consistently present at elevated concentrations, the detection of MTBE is <br /> Isuggestive that the release may have occurred within the last 20 years <br /> • Due to elevated concentrations of petroleum hydrocarbons detected in samples collected from <br /> wells VW-1C, VW-2A and VW-3A, it appears that these wells are within the dissolved <br /> petroleum hydrocarbon "core area" of the plume <br /> I The fluctuation of detected dissolved petroleum hydrocarbons in VW-1C, which is located <br /> in the"core area" over the past four quarters is suggestive of a dissolved hydrocarbon plume <br /> with a heterogeneous distribution of hydrocarbon concentrations within the "core area" itself <br /> • Based upon a plot of depth to ground water and TPH-g concentrations from MW-2, MW-3, <br /> MW-5 and VW-1C during each quarterly event (Appendix C), a positive correlation is <br /> apparent between decreasing ground water depths and decreasing TPH-g concentrations <br /> IFurthermore, the plots suggest an apparent relationship between the "drowned" screened <br /> intervals and decreasing TPH-g concentrations <br /> • Conversely, a general relationship is apparent from VW-1C between decreasing ground water <br /> depths and increasing TPH-g concentrations Furthermore, the plots suggest a general <br /> relationship between decreasing TPH— concentrations once VW-1's screen interval became <br /> Isubmerged <br /> I42 RECOMMENDATIONS <br /> I A Remedial Action Work Plan, dated 03 July 1997, was previously submitted to the PHS-EHD for <br /> a soil vapor extraction/rn-situ air sparging system within the petroleum hydrocarbon "core area" <br /> Upon regulatory approval, installation of the remediation system should commence <br /> Vapor extraction wells VW-1 through VW-3 should be utilized for characterization of ground water <br /> conditions in the"core area" The next quarterly monitoring and sampling is scheduled for September <br /> I1997 <br /> I50 LIMITATIONS <br /> Our professional services were performed using that degree of care and skill ordinarily exercised by <br /> environmental consultants practicing in this or similar localities The findings were based upon <br /> analytical results provided by an independent laboratory Evaluations of the geologic/hydrogeologic <br /> Adf arced GeoEm ironnientai,Inc <br />