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contours associated with the slurry wall groundwater depression (or "shadow") would be <br />expected to decrease uniformly as one moves away from the slurry wall. The closed water level <br />contours noted at well S-13 (Figure 16) are not consistent with groundwater level decreases <br />associated with the slurry wall. <br />5.4.3 Groundwater Level Changes in the Area of Dr. Martin's Pond <br />In light of the complaint lodged by Dr. Martin, it is of particulaz importance to note the <br />groundwater level changes at well L-2, located about 120 feet south-southwest of Dr. Martin's <br />pond and I,400 feet south-southeast of the slurry wall. This well provides an excellent record of <br />the groundwater level changes in the area of the Martin pond. The hydrograph for well L-2 <br />(Figure 17) indicates that the groundwater levels in the area of the pond are highest during the <br />summer irrigation season and lowest during the winter months. This pattern is noted for both the <br />pre- and post- slurry wall periods. The hydrograph shows that the difference in groundwater <br />levels between the irrigation season high and seasonal low water period at well L-2 is about 5 <br />feet. A maximum groundwater level fluctuation of 9 feet was observed at well L-2 in 1998 prior <br />to the installation of the slurry wall. SCIENTECH personnel observed during the summer of <br />2001 that Dr. Martin supplements the normal ("static") pond level during the summer by filling <br />the pond to capacity using an outlet from the irrigation ditch that is adjacent to his pond. Because <br />Dr. Martin's pond is filled to capacity during the summer it serves as a local source of <br />groundwater recharge during the irrigation period. <br />An estimate of the depth of water remaining in Dr. Martin's pond during the seasonal low water <br />period (usually April) prior to and after the slurry wall was installed can be made using the L-2 <br />hydrograph, the approximate ground surface elevation at the pond, and the approximate depth of <br />the pond (which is estimated at about 10 feet below grade). Figure 17 shows the L-2 hydrograph, <br />the estimated ground surface and pond bottom elevations, and the time when the slurry wall <br />construction was initiated. This figure allows the depth of water remaining in the pond at low <br />seasonal water level to be estimated prior to and after the slurry wall was installed. The results of <br />this analysis suggest that the depth of water typically remaining in Dr. Martin `s pond during the <br />seasonal low water period prior to the slurry wall was typically about 1 foot. Since the slurry <br />wall was installed, the pond was dry in February, Mazch, April, and December 2001 which was <br />corroborated by visual observation. <br />This analysis also indicates that the seasonal low pond water level has only have decreased about <br />1 foot since the slurry wall was installed. This estimate is consistent with the estimated - <br />groundwater level decrease of 1.4 feet in the area of the Martin pond shown on Figure 16. <br />Considering the conical shape of the pond (wide at the top and narrow at the bottom) only a <br />13 <br />