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s <br /> ' 1444 MARIPOSA ROAD <br /> WKA No 2938 06 <br /> September 6, 2000 <br /> ' Page 10 <br /> Groundwater flow direction during the last three monitoring and sampling events has been to the <br /> south-southeast with a variable gradient Historical flow direction has primarily been to the east <br /> and southeast with variable gradients Petroleum hydrocarbons in groundwater in the vicinity of <br /> wells MW1,MW3,MW6, and MW7 have not been detected during the last three sampling <br /> events TPH as gasoline has decreased to nondetectable levels in wells MW2 and MW5 and has <br /> slightly decreased in well MW4 since the last sampling event Benzene has not been detected in <br /> any water samples during the last two sampling events During the last sampling event minor <br /> concentrations of MTBE were detected in well MW2 but have decreased to nondetectWe levels <br /> ' in MW3 <br /> ' A groundwater contour map for the latest groundwater monitoring and sampling event performed <br /> on April 18, 200 are presented on Plate 4 A graphical representation of the groundwater flow <br /> ' direction and gradients measured at the site during the past six years is presented on Plate 5 <br /> A summary of depth-to-groundwater measurements and groundwater elevations are included in <br /> Table 2 Analytical results for the water samples are summanzed m Tables 3 through'4 Historic <br /> laboratory reports and chain-of-custody documents are included in various reports presented to <br /> ' San Joaquin County Public Health Services <br /> Sensitive Receptor Survey <br /> ' As part of our site investigation,we performed a sensitive receptor survey for the surrounding <br /> area within a 2,000-foot radius of the property boundary The pnmary potential pathway <br /> ' concerns are surface water bodies or groundwater wells near the site Our surface water body <br /> survey consisted of a windshield survey and a review of the USGS 7 5 Minute Topographic Map <br /> of the Stockton East Quadrangle, California Based on this survey, surface water located within <br /> ' a 2,000-foot radius is Mormon Slough,which is located approximately 500 feet north of the site <br /> In addition to the above windshield survey, our water well survey included a review of California <br /> Department of Water Resources(CDWR)well construction records These confidential records <br /> ' were obtained with the help of staff from CDWR <br /> `�W <br /> WALLACE KOHL <br /> Rec dedpaper &ASSOCIATES WC <br />