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Ms Margaret Lagono <br /> Page 3 of 4 <br />� <br /> Vapor Extraction Wells <br /> Petroleum hydrocarbons were detected in all samples collected from the vapor extraction wells <br /> In paired deep/shallow vapor wells VW11VW2 and VW4/VW5, the wells with the deeper <br /> screened intervals exhibited higher concentrations of target analytes than the shallower wells <br /> ' The onlygasoline ox enates/additives detected in the vapor wells were EDB 1,200 parts per <br /> g oxygenates/additives P ( <br /> billion (ppb)) in vapor well VW 1 and 1,2 DCA (390 ppb in VW 1 and 270 ppb VW4) TPHg and <br /> ' BTEX concentrations are summarized in Table 2 Gasoline oxygenates EDB and 1,2 DCA <br /> concentrations are summarized in Table 3 Attachment B contains laboratory reports and chain of <br /> ' custody documentation <br /> Groundwater Sampling Summary and Discussion <br /> ' • Water levels rose again this quarter Combined groundwater elevation data (Knowles and <br /> ARCO sites) indicate a relatively uniform easterly groundwater flow direction, providing <br /> ' further evidence of contaminant encroachment from the west, across Wilson Way <br /> • TPHg was not detected in wells MWb, MW7, and MW9 through MW 12 and benzene was not <br /> tdetected in wells MW7, MW9, MW 10 and MW 12 <br /> • • Despite increases in some wells this quarter, overall petroleum hydrocarbon concentrations in <br /> 1 the monitoring and vapor extraction wells appear to be generally stable to decreasing <br /> • High levels of MTBE persist in the wells located along the southern portion of the property <br /> ' Although the level of MTBE in well MW 14 decreased significantly this quarter, MW 14 <br /> continues to have the highest concentration (15,000 ppb) of MTBE at the site Since MTBE <br /> is not present in the wells located within the area affected by the onsite gasoline release, its <br /> presence at the site strongly suggests encroachment from an offsite source(s) <br /> ' • EDB and 1,2-DCA appear to be associated with the onsite release <br /> ' VAPOR EXTRACTION SYSTEM ACTIVITIES <br /> VES Operation <br /> ' The soil vapor extraction system was not operated during the second quarter of 2001 pending <br /> direction from PHSIEHD regarding further operation of the system Confirmation borings <br /> sampled during the first quarter indicate that no significant vadose soil contamination remains <br /> roek\4,w\2QM2001 <br /> k <br />