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1 <br /> < I h <br /> 23 November 1998 <br /> AGE-NC Project No 95-0142 <br /> Page 4 of 4 <br /> t 1 I <br /> r , <br /> 4 <br /> • Detectable concentrations of hydrocarbons were present in the down gradient wells MW-4 <br /> and MW-5 The concentration of TPH-g and benzene in wells MW4 and MW-5 have <br /> I i r 1 <br /> increased over=the last quarter <br /> IThe lughest concentration of dissolved petroleum hydrocarbons continues to be in the area <br /> of the documented release (vapor well VW-1), located immediately adjacent to the former <br /> TK1-90 UST " <br /> • _Concentrations of TPH-g and BTEX in the ground water samples collected from vapor wells <br /> VW-1,VW-2 and VW-3 have increased The concentrations of the same analytes detected <br /> in vapor well VW-4 decreased by more than one-half when compared to the results of the <br /> previous quarter - <br /> 5.0. RECOMMENDATIONS <br /> Based upon the data collected to date, AGE recommends <br /> Continued quarterly monitoring, the next quarterly ground water sampling and monitoring <br /> event should be scheduled for December 1998 + <br /> • Installation of an additional ground water momtonng well approximately 35 feet southeast <br /> of VW-1 near the inferred southern margin of the dissolved plume <br /> • Installation of three additional deep aquifer zone ground water monitoring wells,with depth- w <br /> discrete well screens Grab water samples should be collected at a depth of approximately <br /> 45 feet bsg, from the bonngs advanced for the well installations, to aid in definition of the <br /> apparent down gradient extent of dissolved hydrocarbons These samples should be analyzed <br /> for the same constituents as the proposed ground water moiutoring well network <br /> • Installation of additional soil vapor extraction and/or in-situ air spargmg wells needed for <br /> active remediation at the site <br /> i <br /> 6.0. LIMITATIONS <br /> IOur 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 /> Ianalytical results provided by an independent laboratory Evaluations of the geologic/hydrogeoIogic <br /> . conditions at the site for the purpose of this investigation were made from a limited number of data i <br /> Points(I a monitoring-well ground water samples) and subsurface conditions may vary away from <br /> these data points No other warranty, expressed or implied, is made as to the professional <br /> recommendations contained in this report <br /> Advanced GeoEnvironmentai,Inc. <br />