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' r <br /> 15 September 2000 <br /> AGE-NC Project No 95-0103 <br /> Page 3 of 5 <br /> direction ranges from the southwest to southeast within the monitoring well network The average <br /> ' r hydraulic gradient is 0 0125 Figure 3 depicts the ground water elevation contours at the site <br /> ' 3 2 GROUND WATER ANALYTICAL RESULTS <br /> ' TPH-g was detected in samples from monitoring wells MW-1, MW-3, MW-4, MW-5, and vapor <br /> wells VE-1 and VE-6 at concentrations of 4,600 microgram per liter(µg/l), 8,200 µg/l, 3,900 µg11, <br /> 600 µg/l, 2,100 pg/l and 9,600 pg/l, respectively <br /> Benzene was detected in five of the water samples(samples MW-1,MW-3,MW-4,VE-1 and VE-6) <br /> at concentrations ranging from 48 µg/1 in well MW-3 to 1,200 µg11 in well VE-6 The remaining <br /> ' BTE&X compounds (toluene;ethylbenzene and xylenes) were detected in samples MW-1,MW-3, <br /> MW-4,MW-5,VE-I and VE-6 with the highest concentrations occurring in samples MW-4 and VE- <br /> 6 <br /> C <br /> MTBE was detected in the water sample from well MW-I at a concentration of 23 Pg/1 DIPE was <br /> detected in samples MW-1, MW-3, MW-4,MW-6,VE-I and VW-6 at concentrations as high as 47 <br /> µg11 TBA was detected in samples MW-1 and VE-I at 91 µg/1 and 85 µg/l, respectively <br /> EDB and 1,2 DCA were not detected above laboratory reporting limits in any of the ground water <br /> ' samples analyzed <br /> The analytical results of current and previous monitoring well samples are summarized in Tables 2 <br /> ' and 3 The laboratory report of the current ground water sampling data(MAI sample ID Numbers <br /> 44138 through 44145), quality assurance and quality control (QA/QC) data and chain-of-custody <br /> ' form are included in Appendix B <br /> ' 3 3 IN-SITU AIR SPARGING/SOIL VAPOR EXTRACTION T <br /> r <br /> Elevated concentrations of dissolved oxygen were detected in the ground water samples from <br /> ' monitoring well MW-4, vapor extraction well VE-3 and air sparging observation wells ASO-1 and <br /> ASO-2 <br /> the' <br /> Over last q uarter of air injection,the dissolved oxygen ygen concentrations for wells ASO-1, ASO-2 <br /> and VE-3,were measured as high as 66 2%,54 6%and 85 4%,respectively(22 August 2000) We11s <br /> MW-1, MW-4, VE-1, VE-6 and ASO-3 had lower dissolved oxygen concentrations of 16 0%7 <br /> ' 41 4%,9 2%, 10 3%and 9 0%,respectively Sparging rates were measured at approximately 10 scfm <br /> during each monitoring event A minimum pressure of'2 psi was maintained for the air sparging <br /> system (Appendix C) <br /> Advm2eed GeoEnN irunmental,Inc <br /> t <br />