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` xc _ <br /> i tl <br /> The local groundwater gradient is flat and flow rates are slow, <br /> so that the rate of horizontal migration is limited, 3-20 inches <br /> per day, under natural conditions. The direction of groundwater <br /> ' motion was toward RW-1 during its operation, and is now toward <br /> E <br /> temporary recovery well MW-19. <br /> Vertic��_ Did <br /> r �`Q The vertical distribution of subsurface hydrararbon contamination <br /> y <br /> ij <br /> at the site is depicted on Figures 19, 20, 2i, and 22. Figure 19 <br /> shows the vertical distribution of hydrocarbon contamination <br /> alone geologic cross-sectyon A-A'. After gasoline escaped from <br /> the underground tanks, it migrated downslope following the <br /> ` boundary between zones 1 a;id 2. When <br /> r <br /> e ..: <br /> it came to the eroded gap <br /> in zone 2 <br /> , the gasoline dropped directly.to the water table in . i <br /> - <br /> zone 3. Some .of the free product hydrocarbon perched on the <br /> wt-ter table in zone 3 dissolved into the groundwater <br />� gaer and was F <br /> transported horizontally under the prevailing groundwater. flow <br /> gradients. <br /> iy S r <br /> The horizontal extent of the hwdrocarbon contamination is' shown <br /> as :extending dust beyondwell Mw-30, because water analyses have <br /> shown that petroleum hydrocarbons were detected in this well. <br /> Proposed well MW--31 should finish the delineation of zone 3 £ <br /> "" f <br /> contamination.nation. <br /> Yt:ri <br /> ll be , <br /> irilled as soon <br /> as access conditions � <br /> perg'tit. Results of that 'dritling will be filed as an addendum to <br /> �= <br /> this report, per Gary Johnson's suggestion.P. <br /> dddr ._ <br /> t Some hydrocarbons formerly migrated vertically across zone 4 k <br />` through the crass-connected 4811 recovery well (since removed) <br />� t <br /> as [ 17 <br />�t <br /> _I} <br />