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J <br /> 22 February 2000 <br /> AGE-NC Project No 95-0103 <br /> ' Page 3 of 4 <br /> 3 2 HYDROCARBON-IMPACTED GROUND WATER <br /> Eight water samples were analyzed by MAI <br /> • TPH-g was detected in samples from monitoring well samples MW-1, MW-3, MW-4, <br /> MW-5, vapor wells VE-1 and VE-6 at concentrations of 3,900 microgram per liter(ug/1), <br /> ' 6,900 kcg1l, 16,100 ,ug/l, 930µg11, 11,000 ,ugll and 12,000,ug/l, respectively <br /> 1 <br /> • The greatest concentration of hydrocarbons as gasoline were detected at the location of wells <br /> ' VE-1 and MW-4 and toward the west at the location of VE-6 <br /> • Benzene was detected in five of the water samples analyzed at concentrations ranging from <br /> 110 µgll in well MW-3 to 4,900µg11 in wells,MW-4 The most significant concentrations <br /> of toluene, ethylbenzene and xylene were also detected in the water samples collected from <br /> monitoring well MW-4 and vapor wells VE-1 and VE-6 <br /> ' MTBE was detected in the water samples analyzed from well MW-1 at a concentration of <br /> 154gll TBA and DIPE were detected to the water samples from wells MW-1,MW-3, MW-5 <br /> and vapor wells VE-1 and VW-6, at concentrations up to 180 pg/1 <br /> The analytical results of current and previous monitoring well samples are summarized in Tables <br /> 2 and 3 The laboratory report of the current ground water sampling data (MAI sample ID Numbers <br /> 1 28349 through 28356), quality assurance and quality control (QA/QC) data and chain-of custody <br /> form are included in Appendix B <br /> ' 4.0. DISCUSSION/CONCLUSIONS <br /> ' Based on data collected recently at the site and during site remediation, AGE concludes <br /> • The relative ground water elevation at the site decreased 0 38 feet during the last quarter The <br /> ' map of ground water contours indicates an off-site flow toward wells MW-3 and MW-6 <br /> •` Monitoring wells MW-1,MW-2, MW-3, and MW-4 had ground water approximately three <br /> ' to four feet above the top of the screened interval, potentially reducing the effectiveness of <br /> these ground water monitoring wells to characterize the dissolved-phase hydrocarbon plume <br /> in the shallowest ground water <br /> ' The greatest concentrations of petroleum hydrocarbons as gasoline concentrations were <br /> detected in samples collected from well MW-4 and vapor wells VE-1 and VE-6 The lughest <br /> ' benzene concentrations were detected in the sample collected from monitoring well MW-4 <br /> and vapor well VE-6 at the northwest edge of the site <br /> • Fuel additives DIPE, MTBE and TBA were detected in the ground water samples <br /> Advanced GCOLnWronmcntal,lnc <br />