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i <br /> Historical Background <br /> • PACIFIC MINI-MART <br />' 4511 Pacific Avenue, Stockton, California <br /> • Based on a transmissivity value of 205 ft2/day and the extraction well screen thickness equal <br /> to 25 ft (screen interval at EW-1), a hydraulic conductivity value was calculated at <br /> 6144 ft/day, or 0 022 cm/s, a hydraulic conductivity of 0 022 cin/s is consistent with a <br /> screened interval located within a well sorted sand to clean sand <br /> • Laboratory analysis of extracted water during the pumping test detected elevated <br /> concentrations of TPH-g, BTEX and MTBE <br /> On 05 and 06 June 2001 four ground water monitoring wells were installed off-site as part of the <br /> investigation Bonngs MW13 through MW16 were completed as ground water monitoring wells <br /> MW-13 through MW-16 MTBE was detected in the soil samples collected from thirty feet bsg from <br /> borings MW 15 and MW 16,these concentrations maybe more reflective of impacted groundwater <br /> in the pore spaces of the soil than of adsorbed MTBE <br /> The highest concentration of dissolved hydrocarbons quantified as TPH-g,TPH-d and overall BTEX <br /> compounds occurs in the areas east and northeast of the dispenser islands, on-site The highest <br /> concentration of MTBE detected in the ground water occurs in monitoring well MW-11, which is <br /> situated in the median ofPacific Avenue High concentrations of MTBE exist in well MW-11,lower <br /> or non-detectable concentrations in the down-gradient and cross gradient wells defined the dissolved <br /> MTBE plume toward the north and west This may indicate that the dissolved MTBE plume is <br />' detaching from the TPH/BTEX hydrocarbon plume At that time, the dissolved MTBE plume has <br /> not been defined east of well MW-15 and MW-16 <br />' In September and October 2001, a low-flow, ground water extraction and treatment system was <br /> installed at the site The system utilizes the newly installed ground water extraction well on site and <br /> a small volume treatment system As of 16 December 2002, approximately 1,315,454 gallons of <br />' hydrocarbon-impacted ground have been extracted and treated for disposal <br /> 1 <br /> Advanced GeoE nvi ro nmental Inc <br /> 1 <br />