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# , 8820101-R COT-10 contamination found in MW-2 and B-4 is the result of horizontal .spreading 4, from the source during downward migration. The soil contamination in MW-1 at depth could be the result of dissolved -groundwater contamination migrating from beneath the source, or the residuals`from 'a free product plume that may have :been present at one time- on the water table. The significantly higher levels of groundwater contamination in MW-1 th' n �-, MW-2, even though the opposite is true with regard to soil contaminatio , 5� :s would tend to indicate that MW-1 is, in fact, downgradient of the sour e. ' In this case, the gradient- would be to .the west, which is the most pr able r assumption in view of the proximity to the Port of Stockton. It is possible that the release tis fairly old and the main body of the dissolved contaminant plume has migrated' downgradient: Based;on the soil type found in the water-bearing portions of MW-1 and, MW-2 and the assumed low gradient slope, the rate of plume mtigration is expected to be slaw. RECOMMENDATIONS LIn light of the absence of groundwater in Well MW-3`, we recommend that'any additional dissolved phase or soil contamination plume,delineation activities, if so required, be delayed until .after .the first significant rains occur. The anticipated seasonal rise in the water table would then permit a more accurate calculation of the local groundwater gradient and allow the sampling and analysis of groundwater in. MW-3. This, in turn, would provide a better evaluation of the extent of groundwater i contamination beneath the site. In the interim, we suggest that county and j state records be reviewed to establish the location of existing or C , potential groundwater users in the vicinity of the site. ; LIMITATIONS 1 - . The discussions contained herein are based ori the results of the field exploration and laboratory test program described above and the assumption ' 13