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ASS OCIATES INC hydrocarbons A program of quarterly groundwater monitoring and sampling was initiated in March 1994 In August 1995, Smith Technology conducted a subsurface site investigation to further define the extent of contamination in groundwater at the site Smith Technology supervised the installation of monitoring wells MW-4, MW-5, and MW-6 The three new wells were developed and sampled along with the original monitoring wells MW-1, MW-2, and MW-3 Analytical results of groundwater samples from the six monitoring wells indicated the presence of elevated concentrations of petroleum hydrocarbons in the vicinity of wells MW-3 and MW-6, in the northeast corner of the site In November 1998, ATC conducted a subsurface site investigation to evaluate the vertical and horizontal extent of hydrocarbon impacted soil ATC supervised the installation of three soil borings SBI, S132, and SB3 from approximately 30 to 50 feet bgs Analytical results of soil samples indicated the vertical extent of soil contamination had been defined, but the horizontal extent of impacted soil was not fully identified in the northeast corner of the site Site activities are summarized in ATC's Summary Report of Additional Subsurface Investigation, dated January 27, 1999 SAMPLING ACTIVITIES On July 10, 2002, ATC personnel collected groundwater samples from monitoring wells MW-1 through MW-6 The locations of the monitoring wells are shown on Figure 2 Prior to collection of groundwater samples, the depth to water, pH, electrical conductivity, and temperature were measured in the monitoring wells and recorded A minimum of three well casing volumes was purged from each well prior to sampling The wells were allowed to recover and samples were collected from each well using dedicated disposable bailers Purged well water was contained on site in DOT approved 55 gallon drums and labelled for disposal pending receipt of lab results The groundwater samples collected from each well were submitted to Argon Laboratories, a state-certified laboratory (ELAP cert no 2359) located in Ceres, California, for analysis Laboratory analysis consisted of total petroleum hydrocarbons as gasoline (TPHg) utilizing EPA method 8015 and, benzene, toluene, ethylbenzene, total xylenes (BTEX) and methyl tertiary butyl ether (MTBE) utilizing EPA method 8020 Any samples containing detectable concentrations of MTBE were also analyzed for fuel oxygenates by EPA Method 8260 Groundwater well purge and sample logs are contained in Attachment 1 ANALYTICAL RESULTS The samples from wells MW-1, MW-4, MW-5, and MW-6 contained no detectable concentrations of TPHg, BTEX, or MTBE TPHg, ethylbenzene, and MTBE were detected in the sample from well MW-2 TPHg and BTEX were detected in the sample from well MW-3 A w Iwordpro1626051quart1y13QR-2002 doe 2