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• In August 1993, wells MW-1, MW-2, and MW-3 were monitored and sampled Analytical results showed that MW-1 had no measurable concentrations of petroleum hydrocarbons in the groundwater Wells MW-2 and MW-3 contained detectable levels of petroleum hydrocarbons A program of quarterly groundwater monitoring and sampling was begun in March 1994 In August 1995, Smith Environmental conducted a subsurface site investigation to further define the extent of contarnination in groundwater at the site Snuth Environmental supervised the installation of monitonng wells MW4, MW-5 and MW-6 These three new wells were developed and sampled along with monitonng 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 SAMPLING ACTIVITIES On July 9, 1997, groundwater samples were collected by Smith Technology personnel 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 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 Argon Mobile Laboratories (ELAP cert no 1873) for analysis of total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, xylenes (BTEX), and 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 samples collected from wells MW-2, MW-3, and MW-6 The samples collected from wells MW-1, MW-4, and MW-5 contained no petroleum hydrocarbons above the method detection limit MTBE was not detected in any well, although MW3 had a higher detection limit 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, MW-2, MW-3, MW-4, MW-5, and MW-6 on July 9, 1997 Water levels ranged from 22 10 to 22 86 feet below the tops of the well casing elevations, representing an average decrease in the water table elevation of approximately 3 34 feet since April 1997 The water level data were used to develop the groundwater elevation contour map (Figure 2) Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed towards the southeast with a slight mounding effect w 1943731quarpy\3gr-1997 d" 2 • SMTH