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I 1 1 ! I h f 28 April 1998 - AGE-NC-95-0103 ' Page 5 of 9 ' concentrations of 1,100 parts per billion'(ppb, reported as micrograms per liter), 6,300 ppb,43,000 ppb and 120 ppb, respectively ' 7 , ' Benzene was detected in wells MW-1, MW-3 and MW-4 at concentrations of 2 0 ppb, 140 ppb and 15,100 ppb,respectively Benzene was not detected in wells MW-2,MW-5,MW-6 and MW-7 Other BTE&X compounds were detected in these wells at concentrations as high as 6,300 ppb (xylene,, ' MW-4) Ethylbenzene and xylenes were detected in well MW-4 at concentrations of 1,300 ppb Petroleum hydrocarbons were not detected in the samples collected from wells MW-2, MW-6 and the eastern most well MW-7 MTBE was detected only in the ground water samples collected from wells MW-1 and MW-4 at concentrations of 5 3 ppb and 55 ppb, respectively DIPE was also detected in samples collected from wells MW-3 and MW-5 at concentrations of 40 ppb and 85 ppb,respectively ETBE,TBA and TAME were not detected at the site ' The analytical results of current and previous`samples are summarized in Table 2 and Table 3 The laboratory report (MAI sample ID Nos 87641 through 874646 and 87856) and chain-of-custody form are included in Appendix D I a wt 3 3 ANALYTICAL RESULTS OF SOIL SAMPLES TPH-g, BTE&X and oxygenated compounds were not detected in soil samples collected from the f location of well MW-7 Soil samples collected from depths of 15, 20 and 25 feet bsg were analyzed " ' The laboratory reports(MAI Laboratory ID 87747 to 87749), QA/QC report and chain-of-custody are in Appendix E 34 IN-SITU AIR SPARGING E Slightly elevated concentrations of dissolved oxygen were detected in monitoring wells MW-1 and ' 4, # MW-4, and well ASO-2 Dissolved oxygen concentrations in the remaining wells showed slight changes The greatest changes of dissolved oxygen content were observed urmonitoring wells closer to the sparging wells/points I Since the initiation of in-situ air sparging began at the site in April 1997, the average dissolved oxygen concentrations for wells ASO-1; MW-1 and ASO-2 were 102 6%, 78%r and 44 5%, ' respectively Wells MW-2 and MW-4 have had average dissolved oxygen concentrations of 11 2% and 12 7% While the more distal down-gradient wells MW-6, MW-3 and MW-5 have had average+ F dissolved oxygen concentrations of 5 5%,6 1% and 8 3%, respectively The dissolved oxygen data I k Advanced GeoEnvironwntal,inc y , Iil IIS 7 4 i it i f i