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VAT C 1117 Lone Palm Avenue, Suite B <br /> Modesto, CA 95351 <br /> www.atcassociates.com <br /> 209-579-2221 <br /> ASSOCIATES I N C . Fax 209-579-2225 <br /> j Environmental, Geotechnical and Materials Engineers <br /> l � <br /> The shallow groundwater plume appears to be adequately defined in all directions except to the <br /> south, with respect to monitoring wells associated with the subject site. Benzene was detected in <br /> the groundwater sample collected from MW3, and MTBE and 1 ,2-DCA were detected in the <br /> groundwater samples collected from MW3 and MW9. These wells are located in the southern <br /> portion of the site. Monitoring wells MWl and MW8 continue to be the most impacted with <br /> respect to BTEX constituents, and MW3 was the most impacted with respect to 1 ,2-DCA during <br /> the first quarter 2008 sampling event. Assuming that the hydrocarbon plume has commingled <br /> with the hydrocarbon plume associated with the former Apache Plastics facility located south of <br /> the subject site across Fremont Street, then based on laboratory analytical data associated with <br /> groundwater samples collected from the former Apache Plastics facility on March 6, 2008, it <br /> appears the groundwater plume has been defined to the south. Apache Plastics monitoring wells <br /> j MW4 and MW5 are screened at similar depths as the shallow monitoring wells associated with <br /> the subject site. These. wells are generally located south of the subject site and hydrocarbons were <br /> Li{ I not detected in samples collected from these wells on March 6, 2008 . <br /> The intermediate groundwater plume appears to be generally defined to the northwest in the <br /> 1 vicinity of MW12 and MW4, but not well defined in other directions. Monitoring wells MW12 <br /> and MW4 are slightly impacted, and MW5 and MW6 continue to be the most impacted wells. <br /> 1 ,2-DCA was the only analyte of interest detected in intermediate groundwater zone wells <br /> MW18 and MW19 indicating the groundwater plume with respect to 1 ,2-DCA extends east of <br /> the Central Valley Lift Truck parcel. It should be noted that the impacted groundwater below the <br /> Central Valley Lift Truck parcel is likely a result of the known unauthorized release associated <br /> with the former Apache Plastics site located at 2050 East Fremont Street, or possibly <br /> commingling of the Apache Plastics and former Stockton City Taxi Cab plumes. <br /> LI <br /> _I Subsequent to discovery of possible grout intrusion into the well casing which prohibited <br /> development of the well, MW17 was destroyed and replaced. The well destruction and <br /> replacement activities will be discussed in a forthcoming report. <br /> _I <br /> i <br /> i <br /> SII <br /> it <br /> S:\Enviromental\28349Veports\Inv rpt 2008.doc 8 ATC Associates Inc. <br /> i <br />