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u <br /> CLEAKWA'T-ER <br /> G R O U P I N C <br /> Enurronmtntol SC/vices <br /> EHD comments The workplan and addendum were approved by the EHD on December 15, <br /> 1998 <br /> In January 1999, Clearwater supervised the installation of three additional groundwater monitoring <br /> wells (MW-4 through MW-6) to delineate the extent of dissolved-phase contamination and <br /> performed a sensitive receptor survey The results of the investigation indicated that the extent of <br /> sorbed-phase contamination was delineated and existed from approximately 10 to 25 feet bgs near <br /> the former USTs Results of the groundwater samples indicated that the extent of dissolved-phase <br /> contamination remained undelineated downgradient from the former UST system However, high <br /> contaminant concentrations in cross-gradient position of wells suggested that off-site sources may <br /> be contributing to contamination detected beneath the site Initial inquiries suggested and was latter <br /> confirmed that there is existing fuel transport lane in the area if the site, and that it is currently filled <br /> with nitrogen gas Based on this information, Clearwater recommended additional investigation <br /> along South Fresno Avenue to better understand the distribution of contamination and possible <br /> contribution from potential off-site sources The results of this phase of investigation were <br /> presented in Clearwater's Well Installation and Groundwater Monitoring Report - First Quarter <br /> 1999 <br /> In March 2000, Clearwater supervised the completion of one hvdropunch, six soil borings, the <br /> destruction of MW-5, and three of the borings were converted irito monitoring wells (MW-5B, <br /> MW-7, and MW-8) 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 former <br /> UST location to assess the vertical extent of groundwater contamination at 36 feet bgs Three soil <br /> borings were performed to define the lateral extent of soil and groundwater contamination on the <br /> northeastern portion of the site and assess possible off-site sources A total of three soil samples <br /> and one groundwater sample were analyzed from each boring Soil concentrations of TPHg and <br /> BTEX were only detected in boring MW-5B The highest soil concentration of TPHg (1,000 <br /> mg/kg) was detected at 25 feet bgs in MW-5B This sample was also analyzed for TPH as Jet Fuel <br /> and contained 55 mg/kg Detectable concentrations of BTEX were present in soil samples <br /> collected from boring MW-5B at 25 feet and 35 feet bgs MTBE was not detected by EPA method <br /> 8260 in any of the soil samples analyzed Groundwater concentrations of TPHg and BTEX were <br /> detected in borings SB-9, MW-5B, MW-7 and MW-8 The highest groundwater concentration of <br /> TPHg (9,700 gg/L) was detected in MW-5B MTBE was not detected by EPA method 8260 in <br /> any of the groundwater samples analyzed <br /> GROUNDWATER MONITORING AND SAMPLING ACTIVITIES <br /> i <br /> Date of groundwater sampling August 28, 2000 <br /> Wells gauged MW-1 through MW-8 <br /> Wells purged and sampled MW-1 through MW-8 <br /> Analytes tested TPHg/BTEX/MTBE (EPA Method 8015M/8020) <br /> Laboratory Entech Analytical Labs, (Sunnyvale, CA) <br /> Remarks None <br /> CGI-ZB178C-3QT00 2 September 6, 2000 <br />