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I <br /> I I <br /> • The calculated water table elevations were used to construct the groundwater gradient map in <br /> Figure 3 A southwest-trending groundwater high is apparent, and the contours imply that water is <br /> flowing off this high to both the west and south The predominant flow direction is probably <br /> southwest <br /> 3.2 Analytical Results <br /> Hydrocarbon concentrations rose above detection limits in all of the sampled wells except the <br /> domestic well (G-1) (Table 2) This continues a pattern of fluctuating concentrations from quarter <br /> to quarter However, the concentrations are low, generally 100-150 µg/1(parts per billion) except in <br /> GT-10, which has consistently been the most contaminated This quarter, however, a sharp decline <br /> in the diesel concentration was observed in GT-10, from 180,000 µg/1 to only 1,000 µg/l The <br /> decline follows an equally sharp increase in the third quarter, and is therefore probably,not <br /> sustainable <br /> I <br /> 4.0 CONCLUSIONS <br /> The groundwater gradient and flow direction continue to fluctuate over a large range of cbmpass' <br /> directions A northward flow direction has been measured during the first quarter in more than one <br /> year, but the flow direction has tended to reverse and become southward or westward later in the <br /> year This pattern held true iii the third quarter of 2000, when the flow direction was to the south <br /> The bi-directional pattern observed in December suggests that the flow direction may be starting to <br /> reverse again and assume the more northward direction that is common in the winter months <br /> In the previous report, we concluded that purging has little effect on contaminant concentrations, <br /> because concentrations were quite similar to those during the second quarter, even though the wells <br /> were not purged However, the slight increase from non-detect to 100 parts per billion in the fourth <br /> quarter night be attributable Ito the effects of purging in the fourth quarter To further investigate <br /> the effects of purging, all wells will again be purged before sampling during the first quarter of <br /> 2001 <br />