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3.0 RESULTS <br /> 3 1 Depth to Groundwater and Groundwater Flow Direction <br /> The depth to groundwater on September 3 was approximately 30 feet below grade, which <br /> is about 3 feet deeper than in May and 5 feet deeper than in March (Table 1) Using the <br /> three-point method to contour these values yields a groundwater elevation (piezometiic <br /> surface) trap with a uniform gradient of 0 0033 ft/ft (Figure 3), which is approximately <br /> half as steep as the calculated gradient in May In both quarters, as in five of the past six <br /> quarters the flow direction has been to the southeast In the fourth event (first quarter of <br /> this year), the gradient was to the northeast <br /> 3.2 Laboratory Results <br /> Hydrocarbon concentrations in JLM-4 are statistically unchanged since March The <br /> concentration of 1 2-DCA remained at 3 0 parts per billion (ppb), and the TPH-g <br /> concentration rose from less than 50 to 54 ppb Xylene also increased very slightly, from <br /> less than 0 05 ppb to 12 ppb, but this amount of change is not statistically significant All <br /> other analytes were below the detection limit (Table 2) <br /> Concentrations of most analytes decreased considerably in JLM-3 and JLM-5, but MTBE <br /> and 1,2-DCA concentrations were unchanged Whether the declines aie related to the <br /> drop in the water table or to other factors is uncertain Soil samples collected from JLM-3 <br /> . and JLM-5 during drilling contained no detectable hydrocarbons between 30 and 40 feet, <br /> suggesting that the decline in groundwater concentrations this quarter may be related to <br /> the absence of contaminants in the soil at that depth It is thus possible that as the water <br /> table receded below 27 feet, a portion of the hydrocarbons was absorbed by the soil <br /> between 27 and 30 feet, lowering the dissolved concentration <br /> 4.0 DISCUSSION AND CONCLUSIONS <br /> The decline in hydrocarbon concentrations in JLM-3 and JLM-5, and the relative stability <br /> of concentrations at or below the detection limits in JLM-4, is an encouraging sign that <br /> groundwater contamination is minimal below the base of the clay aquitard <br /> (approximately 26 feet) The concentrations detected this quarter are at least 50% lower <br /> than those reported in previous quarters Monitoring should continue into 2004 to <br /> determine whether this change is real and persistent, or merely a one-time aberration <br /> 3 <br />