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Mr. Harlin Knoll <br /> San Joaquin County Environmental Health Division 4PRION <br /> f 1 May 2001 <br /> Page 5 <br /> approximately 20 minutes until the groundwater removed from the well cleared of <br /> Lo sediments. <br /> L A grab water sample was collected from the well in new 40-milliliter glass bottles with <br /> Teflon-lined caps provided by the analytical laboratory. The sample was designated <br /> MW-4 and the sample was collected so that there was no headspace present in the <br /> LW bottle. The samples were delivered to Positive Lab Service of Los Angeles, California. <br /> Soil Sampling and Analytical Results <br /> Soil sampling and analytical procedures were conducted in accordance with Orion's <br /> r <br /> work plan. Details of the drilling and sampling activities are included in Attachment 6. <br /> Five soil samples were collected from the boring and selected soil samples were <br /> analyzed by Positive Lab Service of Los Angeles, California, a State-certified laboratory. <br /> The samples were analyzed for TPHg using modified EPA Method 8015, and for BTEX <br /> and MTBE using EPA Method 8021 . Analytical laboratory reports and chain-of-custody <br /> f forms for the April 2001 drilling activities are included in Attachment 7 and are <br /> L summarized on Table 3. <br /> R Two soil samples were selected and analyzed from the boring at depths of 18 and 25 <br /> Lfeet below grade. Laboratory analysis indicates that TPHg, BTEX, and MTBE were not <br /> detected in any of the soil samples analyzed from the borings. <br /> Summary of the Site Monitoring Program <br /> As directed by the SJCEHD, BFS has complied with the agency request to install a <br /> L downgradient well and collect a fifth round of groundwater samples at the site. Since <br /> monitoring began in January 2000, TPHg decreased from 440 µg/I from previous <br /> groundwater sampling results in MW-2 to 170 µg/I for this round. MTBE changed from <br /> 42 µg/I from the previous groundwater sampling results in MW-1 to 5.0 µg/1 for this <br /> round. Newly installed groundwater monitoring well MW-4 contained non-detectable <br /> Lconcentrations of hydrocarbon constituents in the soil samples collected and only a trace <br /> amount of MTBE at a concentration of 2.4 µg/l in the water sample collected. <br /> LAnalytical data from this effort compared to previous investigation results show the <br /> concentration of hydrocarbon constituents in the soils at the site are below regulatory <br /> i goals or standards. In consideration of the length of time since these tanks were in <br /> L operation, both the SJCEHD and the RWQCB agreed at the 7 March 2001 meeting that <br /> these USTs were not the source for the MTBE found in the groundwater. All groundwater <br /> ' monitoring wells were placed at locations agreed to by the agency to determine the extent <br /> L of soil and groundwater impacts. <br /> 4 <br /> L <br /> SAB FS\STOCKTON\LTR\LTR008.DOC 5/1/01 <br /> Iti- <br />