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A S 5 0 C I A T E 5 I N C 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 These three new wells were developed and sampled along with 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, on 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, SB2, 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 still not defined on 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 January 11, 1999, groundwater samples were collected by ATC personnel from monitoring wells MW-3 and 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 were purged from each well prior to sampling The wells were allowed to recover and samples were collected from each well using dedicated disposable bailers The groundwater samples collected from each well were submitted to Sequoia Analytical (FLAP cert no 1210) for analysis of total petroleum hydrocarbons as gasoline (TPHg), and benzene, toluene, ethylbenzene, total xylenes (BTEX), methyl tertiary butyl ether (MTBE) utilizing EPA methods 8015/8020 Groundwater well purge and sample logs are contained in Attachment 1 ANALYTICAL RESULTS Petroleum hydrocarbon constituents were detected above laboratory method detection limits in the sample collected from well MW-3 The sample from MW-6 contained no detectable concentrations of TPHg, BTEX, or MTBE TPHg and BTEX were detected in the sample from well MW-3 The method detection limit for MTBE was elevated due to dilution factors A summary of analytical results is presented in Table 1 Laboratory data sheets and chain-of- custody documentation are contained in Attachment 2 GROUNDWATER FLOW DIRECTION Water level measurements were collected from wells MW-1 through MW-6 on January 11, 1999 Water levels ranged from 22 62 to 23 42 feet below the tops of the well casings, representing an w162505*aWy\1gr-1999 doe 2