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1 <br />' 28 July 1995 <br /> AGE-NC-95-0134 <br /> Page 6 of 6 <br />' 5.0. CONCLUSIONS & RECOMMENDATIONS <br /> I5 1 HYDROCARBON-IMPACTED GROUND WATER <br /> Monitoring wells MW-8 and NIW-9 were installed to investigate the extent of hydrocarbons in <br /> ground water after completion of vapor extraction MW-8 was installed to replace MW-1, MW-9 was <br /> installed to replace MW-3, well EW-1 is located near MW-2 In 1988, free product was present in <br /> M[W-1 and MW-2 The groundwater flow direction in 1988 was north-northeast However, because <br />' of the installation and operation of the VES and a s'gnificant drop in groundwater depths, no <br /> groundwater monitoring activities were performed between October 1988 and June 1994 <br /> No petroleum hydrocarbons were detected in water samples during the last three monitoring events <br /> This indicates a dramatic decrease in petroleum hydrocarbons since 1988 The process of vapor <br /> extraction in the vicinity of these wells, combined with natural degradation is most likely responsible <br /> Ifor the decrease of petroleum hydrocarbon concentrations to below detectable hrmts <br /> 5 2 HYDROCARBON-IMPACTED SOIL <br /> The PHS/EHD stated in the October 5, 1994 letter that soil "contamination remaining is a threat to <br /> groundwater and further remediation is required " A narrow band of hydrocarbons was encountered <br /> from 30 to 40 feet in the confirmatory borings drilled on June 14, 1994 (CB-1 and CB-2) TPH-g <br /> was detected in borings CB-1 and CB-2 at concentrations up to 2,200 ppm However, no benzene <br /> Iwas detected in any of the samples analyzed, and only low concentrations of toluene, ethylbenzene <br /> and xylenes were detected Therefore, the majority of the most volatile and concurrently the most <br />' toxic fractions of hydrocarbons have been remedlated <br /> A fate and transport modeling program was used to predict the mass of contaminants that will reach <br /> I ground water The results of the model program predicted that the remaining hydrocarbon <br /> compounds are not likely to pose a threat to ground water <br /> I6.0. LIMITATIONS <br /> I Our professional services were performed using that degree of care and skull ordinarily exercised by <br /> environmental consultants practicing in this or sinular localities The findings were based upon <br /> analytical results provided by an independent laboratory Evaluations of the geologic/hydrogeologic <br /> conditions at the site for the purpose of thus investigation are made from a linuted number of available <br /> data points (i a water and soil samples) and subsurface conditions may vary away from these data <br /> . points No other warranty, expressed or implied, is made as to the professional recommendations <br /> contained in this report <br />