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EXECUTIVE SUMMARY <br /> 1� <br /> To augment the existing groundwater monitoring well network, and replace wells that <br /> have been dry due to recent drought conditions, Burlington Environmental Inc installed five <br /> new wells at the Rainbo Baling Company/Earth Grains facility in Stockton, California The <br /> ' new and the previously existing monitoring wells assess the extent of gasoline-impacted <br /> groundwater at the facility and provide information required for eventual remediation <br /> Shallow groundwater at the facility, which is under confined or semi-confined <br /> ' conditions, flows northeasterly at approximately 0 23 ft/d The groundwater surface gradient <br /> is 2 5 x 10-3 ft/ft In March 1994, this shallow groundwater was approximately 55 feet <br /> ' BGS, but has been observed closer to the surface prior to the recent drought <br /> Groundwater at this facility has been impacted by gasoline potentially originating from <br /> an underground storage tank that was removed by Rainbo in April 1987 The extent of the <br /> gasoline-impacted groundwater has been delineated by the monitoring well network at this <br /> facility The cross-gradient limits of gasoline impact are situated near wells MW-4 and <br /> MW-10 to the northwest, and wells MW-5 and MW-12 to the southeast The upgradient and <br /> downgradient extent of impact is defined by wells MW-9 and MW-3, respectively <br /> The concentrations of total volatile hydrocarbons as gasoline in groundwater samples <br /> collected from facility monitoring wells ranged from non-detected to 69,000 micrograms per <br /> liter (µg/L), Benzene concentrations in groundwater samples ranged from non-detected to <br /> 2,000 �cgfL Phase-separated hydrocarbon product has not been detected in any of the wells <br /> ' The extent of any remaining residual gasoline-impacted soil is limited Only one soil <br /> sample collected during this investigation contained petroleum hydrocarbons That one <br /> impacted sample was collected at a depth just below the groundwater table, and was <br /> contaminated by the gasoline-impacted groundwater at that location <br /> 1 <br /> 04/94/121382/125997/STOCKREP REP/1 v <br />