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ate. <br /> MEM ID <br /> .w <br /> The concentration of petroleum hydrocarbon constituents in <br /> w* <br /> i ; groundwater has generally decreased since the installation and <br /> operation of the free product recovery program, Appendix c. <br /> � ! seasonal fluctuations in groundwater quality reflect the effect <br /> of changes in groundwater levels. Higher groundwater levels <br /> wet soil contaminated with adsorbed hydrocarbons which then <br /> F dissolve and contaminate groundwater. <br /> r: <br /> r <br /> f4 The horizontal extent of subsurface hydrocarbon contamination is <br /> 7 4 � shown on Figuresi <br /> 17 and 18 which show the zona 3 and zona 5 <br /> plumes in January, 1988. The striped patterns show the areas of <br /> f benzene contamination in groundwater in each aquifer. Figures 17 <br /> and 18 show that most of the soil and groundwater impacts of the <br /> petroleum hydrocarbon leak at the site are contained in the soils <br /> and groundwater immediately underlying Y g the site. Sail <br /> contamination is confined to a 4=11 area where hydrocarbons have <br /> trickled down to the water table. Groundwater is affected in a <br /> plume oriented northwestward and southeastward from the tank pit r <br /> area. The horizontal distribution of petroleum hydrocarbons in <br /> groundwater is limited to the area immediately underlying the <br /> t JCA site, with,minor movement from beneath the property off-site to j <br /> t � I <br /> $� the southeast. Recent groundwater sampling showed no benzene <br /> - <br /> contamination in wells MW-11, MW-12, MW-22, MW-29, MW-30, and <br /> MW-32. <br /> a <br /> e 15 <br />