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1 Ms Rebecca Setliff tPage 3 of 4 • and chain of custody documentation Graphs depicting TPHg and benzene concentrations over time are included in Attachment D MTBE was the only gasoline oxygenate detected in the sampled wells MTBE was detected in wells ' MW3 (15,000 ppb), MW4 (10,000 ppb), MW7(240 ppb), MW12 (200 ppb) and MW14 (70,000), which are located along the southern portion of the property, and in well MW9 (8 7 ppb), which is located offsite along the north side of Market Street MTBE concentrations in wells MW7 and MW12 increased approximately one order of magnitude since the previous sampling event, and the concentration of MTBE reported in well MW14 is the highest to date These wells are clearly affected by offsite releases and the increasing concentrations in wells MW7 and MW 12 attest to the mobility of the plume EDB was not detected in any monitoring wells sampled, however, 1,2-DCA was present in monitoring wells MW2 and MW12 at concentrations of 35 ppb and 19 ppb, respectively Analytical results for ' gasoline oxygenates, EDB and 1,2-DCA are summarized in Table 3 Attachment C contains laboratory reports and chain of custody documentation ' Vapor Extraction Wells The concentrations of TPHg and benzene reported in vapor well VW2 decreased slightly since the last ' event In vapor well VW3, TPHg decreased while the level of benzene increased No gasoline oxygenate additives, EDB, 1,2-DCA were detected in any sampled vapor wells TPHg and BTEX concentrations are summarized in Table 2 1,2-DCA, EDB and gasoline oxygenate additive concentrations are ' summarized in Table 3 Attachment C contains laboratory reports and chain of custody documentation ' GROUNDWATER SAMPLING SUMMARY AND DISCUSSION • Water levels rose during this quarter Groundwater elevation data continue to show an easterly ' groundwater flow direction TPHg and BTEX concentrations were generally stable to decreasing, however, in monitoring wells ' MW2, MW12 and MW14 TPHg and benzene increased Increases of contamination in these wells appear to be the result of offsite plume encroachment 1 • High levels of MTBE persist in the wells located along the southern portion of the property The concentration in well MW 14 is at its highest level to date The level in well MW7 has increased ' one order of magnitude, and wells MW4, MW7 MW12 and MW14 increasing trends have developed The contamination plume originating at the Top Filling Station is continuing to spread and is now commingling with the Knowles Plume ' • EDB and 1,2-DCA appear to be associated with the onsite release, but are not laterally widespread Concentrations of 1,2 DCA detected in wells MW2 and MW12 are generally consistent with those detected from previous events i 1 ' roeklgmr11gm2002