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s <br /> v+McRs oesr,Eas taiw.vurrs <br /> 1.0 INTRODUCTION <br /> This work plan and quality assurance plan presents the procedures for additional site <br /> investigation activities and groundwater sampling at the San Joaquin County Mosquito and <br /> Vector Control District (SJCMVCD) facility at 200 North Beckman, Lodi, CA The purpose <br /> of this additional site investigation is to further delineate the extent of petroleum hydrocarbons <br /> in soil The purpose of the groundwater sampling is to determine groundwater flow direction <br /> and determine if groundwater has been impacted below an area of known soil contamination <br /> Data generated from the investigation and the groundwater sampling will be used to develop an <br /> updated corrective action plan <br /> 1.1 Site Back round <br /> In 1986, three underground storage tanks (USTs) were removed from the site and soil was <br /> excavated from beneath the USTs to a depth of 31 ft below ground surface (bgs) As a result <br /> of the discovery of petroleum hydrocarbons in soil beneath the tanks, a soil and groundwater <br /> investigation was conducted in 1987 The 1987 investigation consisted of the completion of six <br /> soil borings and the installation of three groundwater monitor wells Petroleum hydrocarbons <br /> were detected in soil to a depth of 31 ft but were not detected in groundwater <br /> In December 1991 a quarterly groundwater sampling program was begun at the facility <br /> Because of the drought related lowering of the regional water table, at the beginning of the <br /> quarterly groundwater sampling program only MW-1 contained enough water to sample, and <br /> another well (MW-4) was installed Groundwater samples were collected through January 1993 <br /> Petroleum hydrocarbons were not detected in groundwater during the sampling program <br /> In July 1994 an additional soil and groundwater investigation was conducted Soil samples were <br /> collected from three borings and two grab groundwater samples were collected from two of the <br /> borings Petroleum hydrocarbons were detected in soil to a depth of 50 ft Petroleum <br /> hydrocarbons were not detected in groundwater samples collectecd from the two borings, <br /> however, a groundwater sample was not collected from the boring with the highest <br /> concentrations of petroleum hydrocarbons in soil <br /> L% \s"Ogvx�r av l <br />