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Geofogicaf Technics Inc. ; 2741 RZrver�kgad fI U 3 f1 96desio,Caffomia 95351 (20 9)53 8-64 2 41 aX#538-5852 Work Plan Additional Soil and Groundwater Investigation ' Super Stop Market rpt Cardoza Enterprises ,dry 290 N. Main St. Manteca, CA Project No 662 2 January 15, 2001 r10 INTRODUCTION In March of 1998 a total of six angle boreholes were hand augured beneath the three existing 8,000 gallon USTs at the site Slight amounts of MTBE, Toluene, and Xylene were detected in the soil sample from B-1 ' On April 29 and May 26, 1998 Cardoza Enterprises was directed by San Joaquin County Environmental Health Department to submit a work plan to determine if residual soil or groundwater contamination exists beneath the tanks (see Figures 1 & 2) Two direct push ' soil borings were installed in August of 1998 Results showed the presence of fuel oxygenate compounds in the soil and BTEX, TPH-G and the fuel oxygenate compounds in the groundwater In March of 1999, the three underground fuel storage tanks and associated product lines and vent lines were removed At that time soil samples were collected and tested according to the regulator's discretion New storage tank and dispenser system was installed and the ' station returned to operation On January 5, 2000, three soil borings were drilled at the site and converted into groundwater monitoring wells Four quarterly sampling/monitonng events have been ' completed since the installation of wells MW-1 through MW-3 Groundwater samples collected from MW-1 and MW-3 have contained elevated concentrations of the gasoline oxygenate MTBE Well MW-2 has not contained contaminant concentrations above the ' laboratory reporting limits The groundwater plume is undefined to the east and south of the site ' 2.0 PROPOSED INVESTIGATION • r