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a <br /> A S S O C I A T E S I N C <br /> GROUNDWATER FLOW DIRECTION <br /> Water level measurements were collected from wells MW 1 through MW4 on December 8, 2000. <br /> Water levels ranged from 24.52 to 25.41 feet below the tops of the well casing elevations, <br /> representing an average decrease in the water table elevation of approximately 0.50 feet since <br /> September 5, 2000. The water level data were used to develop the groundwater elevation <br /> contour map (Figure 2). Assuming that horizontal isotropic conditions prevail, groundwater in <br /> the uppermost aquifer beneath the site flowed towards the east-northeast. The average hydraulic <br /> gradient on December 8, 2000 was calculated to be 0.001 ft/ft or approximately 7.0 ft/mile. A <br /> summary of groundwater monitoring data is presented in Table 1. <br /> ANALYTICAL RESULTS <br /> The groundwater samples collected from wells MW1, MW2, and MW4 contained no detectable <br /> concentrations of TPHg, TPHd, TPHss, or BTEX. The groundwater sample collected from well <br /> MW3 contained TPHg at a concentration of 1,700 parts per billion (ppb). The groundwater <br /> sample from well MW3 also contained TPHss at a concentration of 1,900 ppb and detectable <br /> concentrations of ethylbenzene and xylenes. Analytical results of groundwater samples are <br /> summarized in Table 2. Laboratory data sheets and chain-of-custody documentation are <br /> contained in Attachment 2. <br /> CONCLUSIONS <br /> Concentrations of petroleum hydrocarbons remained nondetectable in wells MW1, MW2, and <br /> MW4. Concentrations of TPHg, TPHss, ethylbenzene, and xylenes in well MW3 increased since <br /> September 2000. The direction of groundwater flow has been consistently east-northeast since <br /> the groundwater wells were installed in December 1998. Groundwater elevations have decreased <br /> since September 2000. <br /> RECOMMENDATIONS <br /> I <br /> Based on the results of the Fourth Quarter 2000 monitoring episode, we recommend the <br /> following: <br /> • Prepare a Closure Report for submittal to the appropriate regulatory agencies. <br /> ATC will begin preparing the Closure Report and it will be submitted by the end of March 2001. <br /> wA l 72951quartlyl4gr-2000.doc 3 <br /> I <br />