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A S S O C I A T E S I N C concentrations of petroleum hydrocarbons Field activities and analytical results were detailed in ATC's Summary Report ofAdditional Investigation, dated October 19, 1998 SAMPLING ACTIVITIES On August 17, 1999, groundwater samples were collected by ATC personnel from monitoring wells MW1 through MW3 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 State-certified Argon Laboratories, Inc (ELAP Cert No 2358) 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) and methyl tertiary butyl ether (MTBE) 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 22,000 parts per billion (ppb) and 600 ppb, respectively TPHg was detected above laboratory detection limits in the samples collected from well MW2 at a concentration of 730 ppb The chromatogram patterns indicated that the concentrations of TPHg contained heavier hydrocarbons The sample collected from well MW1 contained no detectable concentrations of TPHg, TPHd, or BTEX None of the samples contained detectable concentrations of MTBE A summary of analytical results is presented in Table 2 Laboratory data sheets and chain-of-custody documentation are contained in Attachment 2 GROUNDWATER FLOW DIRECTION Water level measurements were collected from wells MWI through MW3 on August 17, 1999 Water levels ranged from 11 59 to 13 02 feet below the tops of the well casing elevations, representing an average decrease in the water table elevation of approximately 2 25 feet since May 1999 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 southwest The average hydraulic gradient on August 17, 1999 was calculated to be 0 0005 ft/ft or approximately 2 6 ft/mile A summary of groundwater monitoring data is presented in Table 1 w\625001quartlyl3gr-1999 doc 2