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ADDITIONAL SOIL AND GROUNDWATER ' INVESTIGATION REPORT AND WORK PLAN ADDENDUM CANEPA'S CAR WASH 248 PARK STREET STOCKTON, CALIFORNIA July 12, 2004 10 INTRODUCTION Condor Earth Technologies, Inc (Condor) conducted soil and groundwater investigation activities from April 14, 2004 through April 19, 2004 at and near Canepa's Car Wash, located at 248 Park Street (site) in Stockton, California (Figure 1, Appendix A) Condor prepared this report at the request of Mr Remo Canepa The soil and groundwater investigation activities were conducted in general accordance with the Work Plan for Additional Sail And Groundwater Investigation by Cone Penetrometer Testing, dated November 1, 2002, prepared by Condor, and approved by the San Joaquin County Environmental Health Department(SJCEHD) on March 18, 2003 The purpose of the work described in this report was to further investigate the lateral and vertical extent of petroleum hydrocarbon contamination in soil and groundwater at the site Five cone penetrometer test (CPT) boring pairs were installed to meet this objective (Figure 2, Appendix A) The lithologic and analytical information from the CPT borings is intended to direct the placement of one or more multi- screened, discrete depth monitoring wells to define the three-dimensional extent of contamination associated with the site This report includes project background information, a description of the fieldwork and laboratory methodology, the results of the soil and groundwater investigation, a summary/discussion of the results of the investigation, and an addendum to the above referenced work plan proposing the installation of ' additional monitoring wells and describing the procedures to install them The work described by this report was conducted under the direct supervision of a California Registered Geologist 2.0 SITE BACKGROUND The site is located in the downtown business district of Stockton, California One 12,000-gallon unleaded gasoline underground storage tank (UST), one 5,000-gallon leaded gasoline UST, and one 5,000-gallon I diesel fuel UST were removed from the site in 1990 According to WHF Environmental Consultants, Inc (WHY), soil samples collected from the UST excavation from approximately 16 feet below the ground surface (bgs) contained elevated concentrations of gasoline and gasoline constituents Between I September 1993 and March 1994, WHF installed six soil borings and seven monitoring wells in and around the site Three of the monitoring wells (MW-1, MW-2, and MW-3) were constructed with a screened interval from 45 to 65 feet bgs Wells MW-4 through MW-7 were constructed with a screened I interval from 40 to 60 feet bgs The screened intervals of monitoring wells MW-1 through MW-7 are submerged below the present groundwater table Beginning in April 1997 Condor implemented a quarterly groundwater monitoring program at the site In the Quarterly Monitoring Report — April 2001, dated May 28, 2001, Condor recommended additional . investigation to further characterize the extent of contamination at the site since existing wells are screened well below the current groundwater table and do not provide sufficient information pertaining �� CONDOR