ARCHIVED REPORTS_XR0002451 - Laserfiche WebLink

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[Z 0 CLEARWATER . G R O U P En vtrvn mentnt Sermcce contamination Concurrently, Clearwater also performed a sensitive receptor survey The results of the investigation indicated that the extent of sorbed-phase contamination was delineated and existed from approximately 10 to 25 feet bgs near the former USTs Analysis of the groundwater samples indicated that the extent of dissolved-phase contamination remained undelineated downgradient from the former UST system However, high contaminant concentrations in cross-gradient positioned wells suggested that off-site sources could be contributing to contamination detected beneath the site Inquiries suggested and later confirmed the existence of a fuel transport line in the area of the site The line was found to be filled with nitrogen gas Based on this information, Clearwater recommended additional investigation along South Fresno Avenue to better understand the distribution of contamination and possible contribution from potential off-site sources The results of this phase of investigation were presented in Clearwater's Well Installation and Groundwater Monitoring Report - First Quarter 1999 In March 2000 Clearwater supervised the completion of one h dro unch six soil born s the P P y P � g � destruction of MW-5, and the installation of three monitoring wells (M W-5B, MW-7, and MW- 8) in three of the soil borings All three wells were placed on the downgradient portion of the plume to help determine the downgradient extent of contaminants The hydropunch was performed in the former UST location to assess the vertical extent of groundwater contamination at 36 feet bgs Three soil borings were taken to define the lateral extent of soil and groundwater contamination on the northeastern portion of the site and assess possible off-site sources Three soil samples and one groundwater sample were analyzed from each bonng Soil concentrations of TPHg and BTEX were detected only in boring MW-5B The highest soil concentration of TPHg (1,000 mg/kg) was detected at 25 feet bgs in MW-513 This sample was also analyzed for TPH as Jet Fuel (TPHjf) and found to contain 55 mg/kg TPHjf is unlikely to be present, but is an indicator of a hydrocarbon range on a chromatographic pattern, not a specific product Detectable concentrations of BTEX were present in soil samples collected from boring MW-513 at 25 feet and 35 feet bgs MTBE was not detected by EPA method 8260 in any of the soil samples analyzed Groundwater concentrations of TPHg and BTEX were detected in borings SB-9, MW-5B, MW-7 and MW-8 The highest groundwater concentration of TPHg (9,700 ZB178C/3rdQtr 2004 Monitoring Rpt 3 October 8,2004