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C.tvv o <br /> A S S O C I A T E S I N C <br /> six monitoring wells Indicated the presence of elevated concentrations of petroleum hydrocarbons in the <br /> vicinity of MW-3 and MW-6, in the northeastern corner of the site <br /> In November 1998, ATC conducted a subsurface site investigation to evaluate the vertical and horizontal <br /> extent of hydrocarbon Impacted soil ATC supervised the installation of three soil borings SBI, S132, and <br /> S133 from approximately 30 to 50 feet bgs Analytical results of soil samples indicated the vertical extent <br /> of soil contamination had been defined, but the horizontal extent of impacted soil was not fully Identified <br /> in the northeastern corner of the site Site activities are summarized in ATC's Summary Report of <br /> Additional Subsurface Investigation, dated January 27, 1999 <br /> SAMPLING ACTIVITIES <br /> On June 23, 2003, ATC personnel collected groundwater samples from monitoring wells MW-1 through <br /> MW-6 The locations of the monitoring wells are shown on Figure 2 Prior to collection of groundwater <br /> samples, the depth to water was measured In the wells and the pH, electrical conductivity, and <br /> temperature were measured in groundwater purged from the wells A minimum of three well casing <br /> volumes was purged from each well prior to sampling The wells were allowed to recover and samples <br /> were collected from each well using dedicated disposable bailers Purged well water was contained on <br /> site in DOT approved 55-gallon drums for disposal pending receipt of lab results <br /> The groundwater samples collected from each well were submitted to Argon Laboratories, a state- <br /> certified laboratory (ELAP cert no 2359) located in Ceres, California, for analyses Laboratory analyses <br /> consisted of total petroleum hydrocarbons quantified as gasoline (TPHg) utilizing EPA Method 801513, <br /> benzene, toluene, ethylbenzene, total xylenes (BTEX) utilizing EPA Method 8021B, and methyl tertiary <br /> butyl ether (MTBE), tertiary butyl alcohol (TBA), di-isopropyl ether (DIPE), ethyl tertiary butyl ether <br /> (ETRE), tertiary amyl methyl ether (TAME), 1,2-dichloroethane (1,2-DCA), 1,2-dibromoethane (EDB), <br /> ethanol, and methanol utilizing EPA Method 8260B Groundwater well purge and sample logs are <br /> contained in Attachment 1 <br /> ANALYTICAL RESULTS <br /> None of the analytes of Interest were detected in the groundwater samples collected from MW-1, MW-4, <br /> MW-5, and MW-6 TPHg, toluene, ethyl benzene, and total xylenes were detected in the groundwater <br /> sample collected from MW-2 at concentrations of 5,300 micrograms per liter (µ/L), 6 5 µ1L, 49 g/L, and <br /> 42 µ/L, respectively TPHg was detected in the groundwater sample collected from MW-3 at a <br /> concentration of 100 µIL A summary of current and historical laboratory analytical results Is presented <br /> in Table 1 Hydrographs of groundwater elevations and analytical data are contained in Attachment 2 <br /> Laboratory data sheets and chain-of-custody documentation are contained in Attachment 3 <br /> GROUNDWATER FLOW DIRECTION <br /> Groundwater level measurements were collected from MW-1 through MW-6 on June 23, 2004 <br /> Groundwater levels ranged from 27 61 to 28 49 feet below the tops of the well casings, representing an <br /> average Increase in the water table elevation of approximately 0 85 feet since October 2003 The water <br /> level data were used to develop the groundwater elevation contour map (Figure 3) Assuming that <br /> . horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site fl_owed6 i <br /> } generally towards the northeast with an apparent slight depression in the vicinity of the former UST area jr- p(Gn <br /> sIenvironmental1626051quartlyl2QK-2004 doc 2 <br />