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v 0 • ASSOCIATE S 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 February 11, 2000, 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 method 8015 modified, and benzene, toluene, ethylbenzene, and xylenes (BTEX) utilizing EPA Method 8020 Groundwater well purge and sample logs are contained in Attachment 1 GROUNDWATER FLOW DIRECTION • Water level measurements were collected from wells MW1 through MW3 on February 11, 2000 Water levels ranged from 10 09 to 1151 feet below the tops of the well casing elevations, representing an average increase in the water table elevation of approximately 2 33 feet since November 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 February 11, 2000 was calculated to be 0 0006 ft/ft or approximately 3 2 ft/mile A summary of groundwater monitoring data is presented in Table 1 ANALYTICAL RESULTS TPHd was detected above laboratory detection limits in the samples collected from wells MW2 and MW3 at concentrations of 10,000 parts per billion (ppb) and 350 ppb, respectively TPHg was detected above laboratory detection limits in the samples collected from well MW2 at a concentration of 300 ppb The chromatogram pattern indicated that the concentration of TPHg contained heavier hydrocarbons The sample collected from well MWI. 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 •1 w 1625001quartlyll qr-2000 doe 2