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Soil and groundwater analysis conducted as part of the initial subsurface investigation in August, <br /> ' 1990 indicated that both soil and groundwater had been impacted by the release Soil samples <br /> collected from borings SBI through SB4 and monitoring well MWI established that the bulk of <br /> ' soil contamination occurred in close proximity to the foinier tank pit and between depths of <br /> approximately 10 and 20 feet below grade Some vertical transport of contamination to the <br /> ' water table had occurred, albeit in very low concentrations, as evidenced by the hydrocarbons <br /> detected at the soil/groundwater interface in MW 1 and the low levels of dissolved hydrocarbons <br /> ' in the groundwater <br /> ' Two subsequent rounds of groundwater sampling from MW1 in 1991 detected very low <br /> concentrations of benzene only It was postulated that, due to it's relative volatility, benzene <br /> ' had been preferentially transported <br /> The recent installation of monitoring wells MW2 and MW3 has provided additional information <br /> regarding the extent of soil and groundwater contamination, both in the spatial and temporal <br /> dimensions Well MW2 essentially twinned soil boring SBI, and MW3 was drilled in immediate <br /> proximity to SB3 Benzene was the only constituent detected below 36 feet in the MW2-SBI <br /> ' pair and the only constituent detected in the MW3-SB3 pair above the capillary fringe Only <br /> very low concentrations were detected in these borings/wells The new data suggests that lateral <br /> ' spreading of contaminants in the soil at the site has not occurred to any appreciable degree since <br /> 1990 <br /> 1 <br /> Vertical transport through the soil to the water table has, however, apparently continued during <br /> ' this time, as evidenced by the increased concentrations of contaminants detected in the <br /> groundwater during May, 1992 as opposed to previous events Downgradient transport of <br /> ' contaminated groundwater has also occurred, as well as apparent cross-gradient transport This <br /> ' apparent cross-gradient transport (ie to MW2) is believed to be related to the intermittent <br /> pumping of the irrigation wells at the site which may alter the gradient direction The soil <br /> contamination detected at the soil/groundwater interface in MW2 and MW3 is related to <br /> capillary action <br /> ' R 052992 LF 9 <br />