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L. <br /> L- GeologicafTechnics Inc. <br /> 2741 Raw J oqa <br /> Modesto,Carfamia 95351 <br /> LW (209)538-6424IFaX#538-5852 <br /> LM Work Plan <br /> 4" Monitoring Well Installation <br /> Former Moresco Property <br /> 16865 Gawne Road <br /> Stockton, California <br /> ' Project No. 251.3 <br /> �. November 4, 1998 <br /> 1.0 INTRODUCTION <br /> The subject property had a 500-gallon capacity underground storage tank (UST) once used <br /> for residential automotive fuel supply. The UST was removed on November 15, 1994 and <br /> significant concentrations of gasoline range petroleum hydrocarbons were detected in a soil <br /> sample collected beneath the former tank cradle at depth of 17.5 feet below ground surface <br /> L. (bgs). This information was reported to the San Joaquin County Public Health Services <br /> Environmental Health Division (SJC PHS/EHD) in the Geological Technics Inc. Tank <br /> v Removal Report, 16865 Gawne Road, dated December 9, 1994. <br /> Lo A subsurface investigation designed to define the vertical and lateral extent of the impacted <br /> area was proposed in the Geological Technics Inc. Site Characterization Work Plan dated <br /> March 14, 1995. The SJC PHS/EHD approved the Work Plan on April 3, 1995. <br /> Lo <br /> An initial subsurface investigation was conducted April 5 to 7, 1995 and a remobilization <br /> v occurred on April 21, 1995. The results of this investigation indicated that the vertical extent <br /> at or near the point of release was defined. The lateral extent remained undefined to the north <br />'i and east. This information was documented in the Geological Technics Inc. Soil Boring <br /> Installation Report dated May 12, 1996. <br /> L. Additional site characterization work was conducted on June 17 & 18, 1996. During this <br /> work three additional soil borings were drilled and soil samples collected. In summary, low <br /> levels of BTEX compounds were found in SB-5 and 6, indicating they were at or very near <br /> Lo the lateral extent of the impacted soil, and relatively high levels of MTBE were detected in <br /> one interval from SB-7. This data and a discussion may be found in Geological Technics Inc. <br /> Site Characterization Report dated October 11, 1996. <br /> 'r In September 1997, one vapor extraction and three passive air recharge wells were installed <br /> at the site. A vapor extraction system, serviced by a Thermal Oxidizer, was installed at the <br /> site and was stated on November 12, 1997. The system ran until January 14, 1998. During <br /> L. this period approximately 85 gallons of gasoline were removed from the subsurface. This <br /> t.. <br />