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"dry" months. No correction was made for any other seasonal variations that might affect <br />groundwater levels. <br />The statistical analysis results are summarized in Table 2 and the figures (Figures A-1 through <br />A-12) shown in Attachment A. Table 2 shows the wells analyzed, the number ofpost-slurry wall <br />groundwater level measurements available for the comparison, the number of groundwater level <br />measurements exceeding either the upper or lower tolerance limit (UTL or LTL), and whether <br />the number of measurements exceeding either the UTL or LTL is a statistically significant <br />increase or decrease. For a groundwater level increase or decrease to be considered statistically <br />significant, at least 4 out of a series of 8 groundwater level measurements must exceed the <br />respective tolerance limit. The comparison criterion was set to achieve a 95 percent confidence <br />that the tolerance interval contained at least 48 percent of the groundwater Level measurements <br />(i.e., that the coverage was at least 48 percent or more). <br />The results shown in Table 2 indicate that wells S-2, S-3, and S-4 have experienced a statistically <br />signiftcant increase in groundwater level since the slurry wall was installed. The results also <br />show that well S-5 has experienced a statistically significant decrease in groundwater level since <br />the slurry wall was installed. This analysis indicates that the groundwater level fluctuations at <br />these wells (S-2, S-3, S-4, and S-5) are significantly different from the fluctuations observed at <br />these wells prior to the slurry wall. Therefore, the slurry wall appears to have affected <br />goundwater levels at wells S-2, S-3, S-4, and S-5. <br />None of the other wells analyzed (wells S-1, S-6, S-7, S-8, L-1, L-2, L3, and L-5) exhibited a <br />statistically significant increase or decrease since the slurry wall was installed. This indicates that <br />the groundwater level fluctuations observed at these wells (S-l, S-6, S-7, S-8, L-1, L-2, L-3, and <br />L-5) since the slurry wall was installed aze not significantly different from the fluctuations <br />observed prior to the slurry wall. Therefore, the slurry wall does not appear to have significantly <br />affected groundwater levels at wells S-1, S-6, S-7, S-8, L-1, L-2, L-3, and L-5. <br />15 <br />