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r <br /> ov..v <br /> �D Q�-- <br /> r� CLEARWATER <br /> G R O U P, I N C <br /> Environmental Services <br /> contamination Concurrently, Clearwater also performed a sensitive receptor survey The results <br /> of the investigation indicated that the extent of sorbed-phase contamination was delineated and <br /> existed from approximately 10 to 25 feet bgs near the former USTs Analysis of the <br /> groundwater samples indicated that the extent of dissolved-phase contamination remained <br /> undelineated downgradient from the former UST system However, high contaminant <br /> concentrations in cross-gradient positioned wells suggested that off-site sources could be <br /> contributing to contamination detected beneath the site Inquiries suggested and later confirmed <br /> the existence of a fuel transport line in the area of the site The line was found to be currently <br /> filled with nitrogen gas Based on this information, Clearwater recommended additional <br /> investigation along South Fresno Avenue to better understand the distribution of contamination <br /> and possible contribution from potential off-site sources The results of this phase of <br /> investigation were presented in Clearwater's Well Installation and Groundwater Monitoring <br /> Report - First Quarter 1999 <br /> 40 In March 2000, Clearwater supervised the completion of one hydropunch, six soil bonngs, the <br /> destruction of MW-5, and the installation of three monitoring wells (M W-5B, MW-7, and MW- <br /> 8) in three of the soil borings All three wells were placed on the downgradrent portion of the <br /> plume to help determine the downgradrent extent of contaminants The hydropunch was <br /> performed in the former UST location to assess the vertical extent of groundwater contamination <br /> at 36 feet bgs Three soil borings were taken to define the lateral extent of soil and groundwater <br /> contamination on the northeastern portion of the site and assess possible off-site sources Three <br /> soil samples and one groundwater sample were analyzed from each boring Soil concentrations <br /> of TPHg and BTEX were detected only in boring MW-5B The highest soil concentration of <br /> TPHg (1,000 mg/kg) was detected at 25 feet bgs in MW-5B This sample was also analyzed for <br /> TPH as Jet Fuel (TPHjf) and found to contain 55 mg/kg TPHjf is unlikely to be present, but is <br /> an indicator of a hydrocarbon range on a chromatographic pattern, not a specific product <br /> Detectable concentrations of BTEX were present in soil samples collected from boring MW-5B <br /> at 25 feet and 35 feet bgs MTBE was not detected by EPA method 8260 in any of the soil <br /> samples analyzed Groundwater concentrations of TPHg and BTEX were detected in borings <br /> SB-9, MW-5B, MW-7 and MW-8 The highest groundwater concentration of TPHg (9,700 <br /> ZB178C/1stQtr2004 Monitoring Rpt 3 April 15,2004 <br />