Laserfiche WebLink
1 <br /> ' Ms Margaret Lagono <br /> Page 3 of S <br /> Vapor Extraction Wells <br /> Vapor wells VW1 and VW3 contained petroleum hydrocarbon concentrations that were similar to <br /> the previous quarter <br /> No gasoline oxygenates, 1,2 DCA or EDB were detected in vapor well VW3, however, 1,2 DCA <br /> ' and EDB were detected in vapor well at (630 parts per billion (ppb)) and 800 ppb, respectively <br /> TPHg and BTEX concentrations are summarized in Table 2 Gasoline oxygenates EDB and 1,2 <br /> DCA concentrations are summarized in Table 3 Attachment B contains laboratory reports and <br /> ' chain of custody documentation <br /> ' GROUNDWATER SAMPLING SUMMARY AND DISCUSSION <br /> • Water levels fell during this quarter Groundwater elevation data continue to indicate an <br /> ' easterly groundwater flow direction <br /> • TPHg was not detected in wells MW7, MW9 and MW12 Benzene was not detected in wells <br /> ' MW 1, MW7, MW9 and MW 12 <br /> 0 Overall, the extent of the plume of groundwater contamination associated with the onsite <br /> '• release is stable and concentrations are decreasing <br /> • High levels of MTBE persist in the wells located along the southern portion of the property <br /> MTBE is not present in the wells located within the area affected by the onsite gasoline <br /> release, its 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 but are not laterally <br /> widespread <br /> • Based upon groundwater flow direction, subsurface lithology, plume geometry, and chemical <br /> composition there appear to be no fewer than 3 distinct plumes of groundwater contamination <br /> ' on the east side of Wilson Way, between Washington Street on the south and Market Street <br /> on the north <br /> ' ARCO Plume The most southerly is a plume of dissolved MTBE located east of the <br /> underground storage tanks located at ARCO Station 5469, 130 S Wilson Way The highest <br /> concentrations are present to wells MWS and MW6 Wells MW1, MW2 and MW3 define the <br /> ' cross-gradient limits of the plume The plume is notable for the nearly complete lack of <br /> TPHg and BTEX compounds despite having high concentrations of MTBE <br /> rceklgmrL3QM2001 <br />