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iS 4 i 25 July 1995 AGE-NC-95-0130 Page 3 of 4 4 2 ANALYTICAL RESULTS OF GROUND WATER SAMPLES TPH-g was detected in samples from MW-2 and MW-3 at concentrations of 420 µg/1 (parts per billion ppb) and 2,800 ppb, respectively Benzene was detected in samples from each well at concentrations up to 930 ppb(MW-3) Toluene, ethyl benzene and xylenes were detected in samples from MW-2 and MW-3 at concentrations ranging from 18 ppb (toluene, MW-2) to 230 ppb (ethyl benzene, MW-3) No TPH-g was detected an the water sample from MW-1 The analytical results of all the ground water samples are summarized in Table 2 The laboratory reports and chain-of- custody are included in Appendix A 5.0. CONCLUSIONS AND RECOMMENDATIONS Ground water gradient calculations indicate that MW-2 has remained the down-gradient well since January 1995 However, the highest concentrations of petroleum hydrocarbons were detected in MW-3 for the second consecutive quarter Petroleum hydrocarbon-impacted ground water has been detected on the property directly to the east of the site, across Wilson Way (Roek property) It appears that ground water flow direction in the vicinity of the site rotates or shifts seasonally from northeast to southeast This shift in ground water flow directions may have caused hte hydrocarbon plumes from both sites to coalesce We recommend performing historical research concerning petroleum products used at the Top Falling property and the Roek property If the research indicates a distinction between petroleum usage at the two sites, then a"fuel fingerprinting" of ground water samples collected from the Top Filling site can then be performed to identify specific petroleum products Further assessment of ground water at the site will be required A work plan has been approved by PHS-EHD for the installation of two addtional wells One well as proposed northwest of MW-1 and a second well as proposed for the southwest portion of the property At least one vapor extraction well and two vapor extra extraction observation wells should also be installed for performance of a feasnbinty study 6.0. LIMITATIONS Our professional services were performed using that degree of care and skill ordinarily exercised by environmental consultants practicing an this or similar localities The findings were based upon analytical results provided by an independent laboratory Evaluations of the geologic/hydrogeologic conditions at the site for the purpose of this investigation are made from a limited number of data