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CL-EX"RWATER <br />' c R o u P <br /> • Environmental Services <br /> 1 <br /> Based on these initial investigation results, the SJCEHD requested monitoring wells be installed <br /> to better define the aerial extent of soil and groundwater contamination After discussion with <br />' Lan Duncan of the SJCEHD, Clearwater submitted the Workplan for Site Investigation dated <br /> November 18, 1998 An addendum to the workplan, dated December 10, 1998 was submitted in <br />' response to SJCEHD comments The workplan and addendum were approved by the SJCEHD <br /> on December 15, 1998 <br /> In January 1999, Clearwater supervised the installation of three additional groundwater <br />' monitoring wells (MW-4 through MW-6) to delineate the extent of dissolved-phase <br /> contamination The results of the investigation indicated that the extent of sorbed-phase <br />' contamination was delineated and existed from approximately 10 to 25 feet bgs near the former <br /> USTs Results of the groundwater sample analyses indicated that the extent of dissolved-phase <br /> contamination remained undelineated downgradient from the former UST system However, <br /> high contaminant concentrations in wells located in cross-gradient positions from the former <br />' USTs suggested that off-site sources may be contributing to contamination detected beneath the <br />' site Initial inquiries suggested, and it was later confirmed, that there is an existing fuel transport <br /> I <br /> line in the area of the site, and that it is currently filled with nitrogen gas Based on this <br />' information, Clearwater recommended additional investigation along South Fresno Avenue to <br /> better understand the distribution of contamination and possible contribution from potential off- <br /> site sources The results of this phase of investigation were presented in Clearwater's Well <br /> Installation and Groundwater Monitoring Report - First Quarter 1999 <br />' On March 8, 2000, Clearwater supervised the completion of one h dro unch six soil borings, <br /> , <br />' the destruction of MW-5, and constructed three additional wells MW-5B, MW-7, and MW-8 <br /> (Figure 2) All three wells were placed on the downgradient portion of the plume to help <br />' determine the downgradient extent of contaminants The hydropunch was performed in the <br /> • former UST location to assess the vertical extent of hydrocarbons Three soil bonngs were <br /> ZB178C RAP 3 May 18,2004 <br />