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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 MW 1 through MW4 on September 5, 2000. <br /> Water levels ranged from 24.00 to 2491 feet below the tops of the well casings elevation, <br /> representing an average decrease in the water table elevation of approximately 1.80 feet since <br /> June 2, 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 <br /> September 5, 2000 was calculated to be 0.001 ft/ft or approximately 7.0 ft/mile. A summary of <br /> 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 110 parts per billion (ppb). The groundwater sample <br /> from well MW3 also contained TPHss at a concentration of 230 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 Ci <br /> MW4. Concentrations of TPHg, TPHss, ethylbenzene, and xylenes in well MW3 remained <br /> approximately the same since June 2000. The direction of groundwater flow has been <br /> consistently northeast since the groundwater wells were installed in December 1998. <br /> Groundwater elevations have decreased since June 2000. <br /> RECOMMENDATIONS <br /> Based on the results of the Third Quarter 2000 monitoring episode, we recommend the <br /> following: <br /> Conduct the Fourth Quarter 2000 groundwater monitoring and sampling of wells MW 1 <br /> through MW4 and analyze samples for TPHg, TPHd, TPHss, and BTEX. <br /> Groundwater monitoring activities will be conducted for one more quarter. If concentrations <br /> remain approximately the same or decrease, ATC will recommend site closure. <br /> wA)72451goartly\3gr-2000.doc 3 <br />