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n ASSOC IATES INC concentrations of petroleum hydrocarbons Field activities and analytical results were detailed in ATC's Summary Report of Additional Investigation, dated October 19, 1998 SAMPLING ACTIVITIES On November 20, 1998, groundwater samples were collected by ATC personnel from monitoring wells MW 1 through MW3 The locations of the momtonng wells are shown on Figure 2 Pnor to collection of groundwater samples, the depth to water, pH, electrical conductivity, and temperature were measured in the monitoring wells and recorded A nummum 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 State-certified Sequoia Analytical (FLAP Cert No 1210) for chemical analysis of total petroleum hydrocarbons as gasoline (TPHg) and total petroleum hydrocarbons as diesel (TPHd) utilizing EPA methods 8015 modified, and benzene, toluene, ethylbenzene, and xylenes (BTEX) utilizing EPA methods 8020 Groundwater well purge and sample logs are contained in Attachment 1 ANALYTICAL RESULTS TPHd was detected above laboratory detection limits in the samples collected from wells MW2 and MW3 at concentrations of 47,000 parts per billion (ppb) and 1,000 ppb, respectively TPHg was detected above laboratory detection limns in the samples collected from wells MW2 and MW3 at concentrations of 790 ppb and 120 ppb, respectively Benzene, toluene, and xylenes were detected only in the sample collected from well MW2 The sample collected from well MW 1 contained no detectable concentrations of TPHg, TPHd, or BTEX A summary of analytical results is presented in Table 2 Laboratory data sheets and chain-of-custody documentation are contained in Attachment 2 I GROUNDWATER FLOW DIRECTION Water level measurements were collected from wells MW1 through MW3, on November 20, 1998 Water levels ranged from 11 15 to 12 59 feet below the tops of the well casing elevations, representing an average decrease in the water table elevation of approximately 1 89 feet since August 1998 The water level data were used to develop the groundwater elevation contour map (Figure 3) Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed towards th south-soot west The average hydraulic gradient on November 20, 1998 was calculated to be 0 0003 ft/ft or approximatelt�ff A summary of groundwater monitoring data is presented in Table 1 w 1625001quartly14q-1998 doe 2