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WORK PLAN <br /> FORMER CHEVRON SS 9-1918 <br /> 45 EAST HARDING WAY <br /> STOCKTON,CALIFORNIA <br /> 1. INTRODUCTION AND SCOPE <br /> Chevron U.S.A. Inc. retained EA Engineering, Science, and Technology, Inc. (EA) to <br /> install monitoring wells at former Chevron SS 9-1918,45 East Harding Way, Stockton, <br /> California. Between 7 and 11 November 1988, EA supervised the drilling of six soil <br /> borings that were completed as monitoring wells. The wells were installed by Spectrum <br /> Exploration Inc. The results of this investigation indicate the need to install additional <br /> monitoring wells to detem-jine the extent of ground-water contamination and to drill soil <br /> borings that will be completed with equipment to be used eventually for active soil venting. <br /> This work plan summarizes briefly the results of the initial subsurface investigation and <br /> outlines the work to be appended to the original permit to install monitoring wells that was <br /> issued to Chevron on 4 November 1988. <br /> EA was originally retained by Chevron to conduct a soil vapor contaminant survey <br /> (SVCA)on the site. The SVCA was completed 18 November 1987 when the service <br /> station was still dispensing gasoline. The service station formerly located at this address <br /> was demolished, and the underground tanks were pulled on 24 February 1988. Petroleum <br /> hydrocarbon contamination was identified visually in the soils beneath the tanks and <br /> confirmed chemically by analyses of soils stockpiled for aeration during excavation. Soils <br /> were excavated from the tank pit to a depth of approximately 20 feet, a depth that could be <br /> functionally reached by the excavation equipment. <br /> The current subsurface investigations at this site have been more completely reviewed in a <br /> problem assessment report that has been prepared for Chevron U.S.A. Inc. to be <br /> forwarded to San Joaquin County Environmental Health and the Central Valley Region of <br /> the Regional Water Quality Control Board. <br /> 2. THE CURRENT SUBSURFACE INVESTIGATION <br /> The excavation was backfilled in early November 1988 to remove any potential hazard, and <br /> six monitoring wells were installed on the site(Figure 1). The soil borings were drilled to <br /> depths between 41 and 50 feet with an Acker rotary drill using 10 inch outside-diameter, <br /> hollow-stem auger under contract from Spectrum Exploration Inc. (C57 license number: <br /> 512268). Water was first encountered in the borings between 36 and 43 feet. Ground <br /> 1 <br />