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1 <br /> Mr Ron Rowe <br /> Page 3 of 5 <br /> ' In addition, samples from wells, MW 1 through MW 11, and MW 13 were analyzed for oxygenates, <br /> P <br /> 1,2 DCA, and EDB (well MW 12 was inaccessible) Oxygenates were not detected in wells <br /> MWI, MW2, MW6, MW8, MW10, or MW13 1,2 DCA was detected in wells MW2, MW9, <br /> MW 10 and MW 11, with levels that ranged from 6 8 ppb (MW9) to 260 ppb (MW2) No <br /> detectable concentrations of EDB were found in any site wells MTBE was detected in wells <br /> MW3 and MW4 at concentrations of 3,800 and 1,400 parts per billion (ppb), respectively and in <br /> wells MW7 and MW9 at levels of 33 and 27 ppb, respectively The source of MTBE in these <br /> wells is believed to be from offsite releases DIPE was detected in wells MW5 and MW11 at <br /> concentrations of 37 ppb and 9 5 ppb respectively DIPE, TBA, ETBE and TAME were not <br /> detected in any of the samples collected from the other wells Oxygenate, EDB, and 1,2 DCA <br /> ' analytical results are summarized in Table 3 <br /> Vapor Extraction Wells <br /> ' Groundwater samples were collected from vapor wells VW1 and VW3 through VW6 (VW2 was <br /> dry) Petroleum hydrocarbons were detected all samples collected from the vapor extraction <br /> wells Concentrations of TPHg ranged from 750 ppb to 180,000 ppb in vapor wells VW4 and <br /> ' VW1, respectively Benzene ranged from 1 8 ppb in well VW5 to 22,000 ppb in well VW1 <br /> Levels of petroleum hydrocarbons in the vicinity of the vapor wells appear to be stable, however, <br /> TPHg in well VW3 decreased an order of magnitude It should be noted that the VES never <br /> operated on VW1 or VW4 because the screens in those wells have been submerged since the <br /> inception of vapor extraction The VES has not been in operation since January 3, 2000 The <br /> system was shut down pending direction from PHS/EHD TPHg and BTEX concentrations are <br /> summarized in Table 2 <br /> Samples from vapor extraction wells VW1 and VW3 through VW6 were also analyzed for <br /> ' oxygenates, 1,2 DCA and EDB 1,2 DCA was detected in well VW4 at a concentration of 34 <br /> ppb This was the only fuel additive detected in any vapor well, however, MDLs were elevated <br /> due to dilution Oxygenate concentrations are summarized in Table 3 <br /> Groundwater Sampling Summary and Discussion <br /> MTBE was detected in well MW4 for the eleventh consecutive quarter MTBE was also detected <br /> in well MW3, located downgradient of MW4, for the ninth consecutive quarter TPHg and <br /> ' BTEX concentrations remained high in MW4 during this sampling event and showed a significant <br /> increase in MW3 Benzene, toluene and MTBE were detected in MW7, located north of well <br /> MW3 MTBE concentrations have increased for the third consecutive event suggesting the <br /> ' formation an increasing trend In well MW11, located to the east of wells MW3 and MW7, <br /> toluene and xylenes were detected for the first time <br /> Dissolved contaminants present in groundwater from wells MW3, MW4, MW7 and MW11 <br /> appear to be related in large part, if not entirely, to offsite releases The sudden appearance of <br /> MTBE and petroleum hydrocarbons in these wells, the discernable downgradient movement of <br /> roeklgmrl2QM2000 <br />