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24 November 1997 <br /> AGE-NC-95-0103 <br />' Page 4 of 6 <br />' MW-2, MW-5 and MW-6 <br /> Other BTE&X compounds were detected in these wells at concentrations as high as 12,000 ppb <br />' (toluene, MW-4) Ethylbenzene and xylenes were detected in MW-3 at concentrations of 380 ppb <br /> and 400 ppb, respectively Petroleum hydrocarbons were not detected in the samples collected from <br /> wells MW-2 and. MW-6 <br /> MTBE was detected in MW-1 MW-3 and 1\4W-4 at concentrations of 390 ppb, 6 ppb and 360 ppb, <br /> respectively, by EPA Method 8020 <br />' The analytical results of current and previous samples are summarized in Table 2 The laboratory <br /> report (MAI sample ID Nos 80094 through 80099) and chain-of-custody form are included in <br />' Appendix C <br /> 3 IN-SITU AIR SPARGING <br /> Elevated concentrations of dissol,,ed oxygen were detected in monitoring wells MR,-1 and MW-4, <br /> as well as in observation wells surrounding the ASO-1 well on the site Dissolved oxygen <br /> concentrations in the remaining down-gradient wells showed smaller changes The greatest changes <br /> in dissolved oxygen content was observed in monitoring wells closer to the sparging well/points The <br /> dissolved oxygen data is summarized on Table 3 <br /> Sparging rates were measured at approximately 10 scfm during each monitoring event A pressure <br /> of approximately 15 psi was maintained for the air sparging flow rate <br /> _34 SOIL VAPOR EXTRACTION <br />' The SVE unit operated at varying rates during the observation period Extraction flow rates were <br /> calculated to range from 150 to 160 scfm Typically, the operation averaged 150 scfm during the <br /> period Operation of the unit was attempted at 200 scfm, the maximum operational rate of the unit, <br /> however the unit was noted to automatically shut off, apparently to prevent the catalyst beds from <br /> deteriorating <br /> An induced vacuum (negative pressure) of approximately 25 to 30 inches of water was measured in <br /> the piping between the blower and extraction wells The radius of influence at the well-heads was <br /> noted to range from 0 05 inches of water at well MW-2 and MW-4 to 35 inches of water at ASO-3, <br /> adjacent to VW-1 <br />