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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 MW1 through MW4 on June 2, 2000. <br /> Water levels ranged from 22.22 to 23.10 feet below the tops of the well casings elevation, <br /> representing an average increase in the water table elevation of approximately 0.36 feet since <br /> April 2000. The water level data were used to develop the groundwater elevation contour map <br /> (Figure 2). Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost <br /> aquifer beneath the site flowed towards the northeast. The average hydraulic gradient on June 2, <br /> 2000 was calculated to be 0.001 ft/f( or approximately 5.3 ft/mile. A summary of groundwater <br /> 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 160 parts per billion (ppb). The groundwater sample <br /> from well MW3 also contained TPHss at a concentration of 150 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. The concentration of TPHg remained approximately the same, the concentration of <br /> TPHss decreased in well MW3, and the concentration of TPHd remained nondetectable in well <br /> MW3. The direction of groundwater flow has been consistently northeast since the groundwater <br /> wells were installed in December 1998. Groundwater elevations have increased since April <br /> 2000. <br /> RECOMMENDATIONS <br /> Based on the results of the Second Quarter 2000 monitoring episode, we recommend the <br /> following: <br /> Conduct the Third Quarter 2000 groundwater monitoring and sampling of wells MW1 <br /> through MW4 and analyze samples for TPHg, TPHd, TPHss, and BTEX. <br /> Groundwater monitoring activities will be conducted for two more quarters, if concentrations <br /> remain approximately the same or decrease, ATC will recommend site closure. <br /> } <br /> w:1172951quan1y12gr-2000.doc 3 <br />