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r . 22 November 1999 F AGE-NC Project No 95-0103 Page 3 of 5 • TPH-g was detected in samples from monitoring well samples-MW-1,MW-3, MW-4,MW- _ ' 5, vapor wells VE-I and VE-6 at concentrations of 1,500 microgram per Mer(µg11),,8,900 kg/l, 9,100 µg/l, 1,200µg/1, I0,000µg/1 and 9,000 µg11, respectively • ` The greatest concentration of hydrocarbons as gasoline were detected at the location of wells VE-1,and MW-4 and toward the west to the location of VE-6 • Benzene was detected in five of the water samples analyzed at concentrations ranging from 95 49l1 in well MW-3 to 1,700 12g/1 in wells MW-4 and VE-6 ,The most significant concentrations of toluene, ethylbenzene and xylene were also detected in the water samples ' collected from wells MW-4 and vapor wells VE-I and VE-6 ti MTBE was detected in three of the water samples analyzed(wells MW-1, MW-3, MW-4) at concentrations ranging from 2 0µg/1 to 13 ugll TBA and DIPE were detected in die same water samples, and in the well VE-1 sample, at concentrations up to 89 µg/I The analytical results of current and previous monitoring well samples are summanzed in Tables 2 and 3 The laboratory report of the current ground water sampling data(MAI sample ID Numbers '• 22917 through 22924), quality assurance and quality control (QA/QC) data and chain-of-custody form are included in Appendix B y ,< ' 4 0. DISCUSSION/CONCLUSIONS Based on data collected recently at the site and during site remediation, AGE concludes ' In-situ air sparging (IAS) and soil vapor extraction operated on the site for approximately eight quarters Over this period a calculated minimum of 409 gallons of gasoline had been removed ' A population of biodegrading micro-organisms exists on the site that promotes degradation of the hydrocarbons These organisms were not detected in the off-site sample analyzed (December I998) • A reduction of hydrocarbon concentrations in samples collected from om both on-site and off- site was demonstrated through confirmation soil and water sampling The lack of detection ' of benzene in samples from CHP I, CHP2, CHP3, CHP7, CHP8 and CHP 9 limit the lateral extent of the benzene,impact to the areas under the budding,the north and western ends of ' the site and an area extending 140 feet west of the site • The relative ground water elevation at the site decreased 1 5 feet over the last quarter The map of ground water contours indicates an off-site flow toward wells MW-5 and MW-2 Advanced CcoEn ironmental,Inc " 1