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CLEARWATER <br /> C R O U P, I ISI C <br />! 1.0 INTRODUCTION ' <br /> This 'report presents the results of groundwater monitoring performed by <br />! Clearwater Group, Inc (Clearwater) on December 21, 1994 at 4555 North Pershing <br /> Avenue in Stockton, California The location of the site is shown on Figure 1 The <br /> tasks performed during this phase of work included groundwater gauging, well <br /> purging and groundwater sample collection <br />' 2.0 BACKGROUND <br /> The site (Figure 2) is currently unoccupied and principally utilized as a two-lane <br /> driveway providing access to an adjacent shopping center It was formerly operated <br /> as a cardlock refueling station <br /> Previous investigations have been performed at the site by TreaTek, Inc , TMC <br /> Environmental, Inc (TMC) and McLaren/Hart Nine soil borings were drilled by <br /> TMC to a maximum depth of 31 feet below grade surface (bgs) in June 1991 Analysis <br /> of soil samples collected from the borings indicated the presence of gasoline <br /> contamination at a depth of approximately 25 feet bgs This depth corresponds to <br /> the groundwater elevation seasonal maximum. Three underground fuel storage <br /> tanks (USTs) one leaded gasoline, one unleaded gasoline and one diesel, were <br /> excavated and removed from the site by TreaTek, Inc , on January 8, 1992 <br /> On November 3 through November 5, 1992, McLaren/Hart installed five <br /> groundwater monitoring wells (MW-1 through MW-5) to a maximum depth of 40 <br />' feet bgs MW-1 through MW--4 were installed along the perimeter of the former <br /> tank farm MW-5 was installed in the inferred downgradient direction Four <br /> groundwater monitoring events were subsequently performed by McLaren/Hart. � <br />' Analytical results from these events indicate the presence of gasoline and/or BTEX <br /> compounds in samples collected from all the monitoring wells except MW-5 <br /> Benzene has been detected in groundwater samples collected from MW-2, MW-3 <br />' and MW-4 Concentrations of benzene have consistently been highest in MW-4 <br /> with a concentration of 430 parts per billion (ppb) in the sample collected on June 4, <br /> 1993 <br /> r <br /> r <br /> D-103 QMR 1 February 2, 1995 <br /> 1 <br />