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ADDITIONAL SUBSURFACE IN <br /> Ile C VESTIGATION <br />' SUMMARY REPORT <br /> Speedy Mart <br /> 8200 N. Highway 99, Stockton, CA <br /> 1 <br /> 1.0 EXECUTIVE SUMMARY <br /> Ground Zero Analysts, Inc (Ground Zero) has prepared tins report to describe the installation of <br /> five groundwater monitoring wells and to summanze the analytical results of soil and groundwater <br />' samples collected from the wells Four shallow groundwater monitoring wells (MWS, MW6, <br /> MW7, MW8) and one deeper monitoring well (MW9(B)) were installed to further investigate the <br />' lateral and vertical extent of groundwater contamination beneath the site The wells were installed, <br /> developed, and sampled in October 2000 <br /> The shallow wells were drilled and installed to a depth of approximately 72 feat below ground <br />' surface (bgs) using a drilling ng equipped with hollow stem augers, and were designed to allow <br /> access to the shallow aquifer beneath the site for collecting groundwater elevation data and <br /> groundwater samples The shallow groundwater beneath the site was initially encountered at a <br /> depth of approximately 57-58 feet bgs The monitoring wells were screened from a depth of <br /> approximately 52-72 feet bgs Analytical results collected from the newly installed shallow wells <br /> indicate that the lateral extent of groundwater contamination is essentially defined in most <br />' directions However, the extent of dissolved methyl tert butyl ether (MTBE) has not yet been <br /> defined to the north and northeast A groundwater sample collected from the northernmost well <br />' (MW6) in October 2000 contained 20,000 parts per billion (ppb)MTBE <br /> Monitoring well MW9(B) was installed to a depth of approximately 130 feet to access a deeper <br /> water bearing zone beneath the site The pilot hole for well MW9(B) was drilled using a mud <br /> rotary drilling rig Soil was sampled continuously from a depth of approximately 70 feet bgs to <br /> 135 feet bgs using a 94-millimeter barrel sampler in order to identify deeper water bearing zones <br /> The well was installed in a water-bearing sand layer encountered between the depths of 122 and <br /> 130 feet bgs (the 120-foot aquifer) No other water-bearing sands were encountered between the <br /> depths of 70 and 135 feet bgs No gasoline constituents were detected in the water sample <br /> collected from well MW9(B) <br /> data/groundzeJtuleburg/reports/mud—has_wel lrepmt.doc <br />