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11 <br /> SIERRA <br /> 1. INTRODUCTION <br /> 1.1 Scope of Work <br /> To evaluate the presence or absence of hydrocarbons directly downgradient of the former <br /> underground storage tanks, Sierra Environmental Services (SES) installed one monitoring well <br /> (MW-6) The location of the monitoring wells are shown on Figure 2 (Appendix A) The following <br /> outlines the scope of work for this investigation <br /> 1 Prepare a site safety plan specific to this investigation based on past and present <br /> site use <br /> 2 Abandon one previously existing monitoring well (MW-1) <br /> 3 Drill one soil boring for hydrogeologic description and for possible chemical <br /> analysis Survey soil samples from the boring in the field with an organic vapor <br /> meter (OVM) to determine whether volatile hydrocarbons are present in the <br /> samples Use OVM readings and field observations to select soil samples for <br /> analysis Analyze the soil samples for total purgeahle petroleum hydrocarbons as <br /> 0 gasoline [TPPH(G)), and benzene, toluene, ethylbenzene and xylenes (ErrE) ) <br /> 4 Install one 2-inch diameter monitoring well in the boring <br /> 5 Develop the well <br /> 6 Survey the top of casing elevation of the new well and measure depth to ground <br /> water in allwells Using the previously existing and new survey data and the water <br /> level data, verify the ground water flow direction and gradient at the site <br /> 7 Arrange for disposal of the drill cuttings and well purge water <br /> 8 Report the results <br /> 12 Background <br /> The following information was compiled from the Groundwater Technology (GTI) report <br /> prepared for this service station February 27, 1987 ` The underground storage tanks were <br /> ' Groundwater Technology February 27 1987 Report of Subsurface Investigation, Chevron Service Station#9- <br /> 6171 Stockton California Consultants report prepared for Chevron, 8 pages <br /> Page 2 <br />