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from both KF-1 and KF-2 are typical of fresh, unmodified gasoline, whereas the chromatogram from <br /> KF-3 is somewhat bimodal, being rich in both light-end and heavy-end gasoline hydrocarbons. <br /> 5.0 CONCLUSIONS AND RECOM ENDATTONS <br /> As noted in the April 1995 quarterly report, increased gasoline concentrations in all three monitoring <br /> wells between December 1994 and March 1995 coincided with a rise in the groundwater table and an <br /> increase in the groundwater flow rate. By October, the water table had dropped below its March level <br /> and the flow rate (as reflected in the gradient) had decreased to less than its December rate. These <br /> latter changes coincided with a decrease in contaminant concentrations, particularly in KF-3. Three <br /> quarters of monitoring data are insufficient to draw reliable conclusions regarding the significance of <br /> these changes, which could be due to seasonal variations (whch are quite comrlon), eastward <br /> migration of the contaminant plume, or other causes. Consistent, timely monitoring on a quarterly basis <br /> through 1996 will be needed in order to establish a decipherable pattern in contaminant concentrations. <br /> The data do strongly suggest, however, that groundwater contamination extends off site to the north <br /> and east, beneath.the adjacent residential property. We therefore recommend that additional drilling be <br /> done to collect grab samples of the groundwater and delineate the extent of the contamination. When <br /> the downgradient extent has been defined, two or more monitoring wells should be installed to <br /> determine whether the contaminant plume is migrating in the downgradient direction. <br /> 4 <br />