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After gasoline escaped from the underground tanks , it migrated <br /> downslope following the boundary between zones 1 and 2. When it <br /> carne to the eroded gap in zone 2, it dropped directly to the <br /> water table in zone 3. Some of the hydrocarbon perched on the <br /> water table it zone 3 dissolved into the groundwater. <br /> Hydrocarbons may have migrated into zone 5 through an eroded <br /> channel where zone 4 is missing (off this cross section) , or <br /> through the multicompleticn monitoring wells , such as MW-21 and <br /> € RW-1, in which the well screens are com eted through zone 4. <br /> The amount of dissolved hydrocarbon t has migrated into zone 5 <br /> _14- <br /> Is considered to be small based one to ntaminant . <br /> concentrations observed in wells MW-12, and MW-20. { <br /> Geologic cross. section 3-B',;° Fi a 9, depicts the vertical # <br /> �-' variation of soils and t.h j. ution of co taminants along a <br /> r west to east section.': kcal and hydrological zone <br /> I i <br /> relationships are lar those on cross section ASA' . <br /> Gasoline migrated down a to the paled-channel which removed 1 <br /> zone 2- and percolated downward until it reached the saturated <br /> p <br /> portion of the zone 3 aquifer. Here the free product accumulated <br /> ,S on <br /> the eater table surface and dissolved into groundwater. --; <br /> k <br /> i' section S-9' suggests that a paleo-channel has removed zone 4 <br /> near the .SW:.edSe of the site. Zones 3 and 5 are directly <br /> connected by this channel . Some migration of dissolved <br /> constituents' zone 3 into zone 5 may have occurred through <br /> the pos ulated channel near MW-1 and MW 15 and through the € <br /> multiple zone completion wells at the site. The extent of this r <br /> zone 5 .contamination is considered to be insignificant. ; <br /> t <br /> �}FF <br />