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Backcrround <br /> The site includes three 12, 000 gallon steel underground storage <br /> tanks Presently, the tanks store regular unleaded, super <br /> unleaded, and premium unleaded gasoline USA records indicate no <br /> Significant loss or gain in the inventory The station has three <br /> service islands, each with a vapor recovery system <br /> USA Gasoline Corporation has installed 10 monitor wells in the <br /> course of the investigation of this site Six of these wells are <br /> located within the USA property boundaries and four wells are <br /> located to the south in a downgradient direction (see Figure 3) <br /> After the existing wells were in place (excluding MW8) , a Problem <br /> Assessment Report was prepared December 5 , 1989 This report was <br /> included in Appendix A of the Quarterly Monitoring Report of <br /> September 24 , 1991 It presented Soil Boring analysis, Ground <br /> water analysis, Ground water flow direction, Aquifer test data <br /> with an estimate of transmissivlty and hydraulic conductivity, <br /> and an evaluation of the zero line of contamination <br /> On February 8 , 1993 , MW8 was installed eight feet southeast of <br /> the tank field This location was in a hydraulic downgradient <br /> direction from the tank field (see Figure 3) A Limited Drilling <br /> Report was prepared on February 25, 1993 to document the methods <br /> and procedures used to construct the well This report was <br /> included as Appendix C of the May 4 , 1993 Quarterly Monitoring <br /> Report The well was sampled for the first time on March 31 , <br /> 1993 <br /> GEOLOGY <br /> The deposits under the site are Recent to Pleistocene age <br /> alluvium and consist of lenticular silt, sand, gravel and clay <br /> representing a heterogeneous fluvial environment The Problem <br /> Assessment Report for this site (Appendix A of the Quarterly <br /> Monitoring Report for September 24 , 1991) details the local and <br /> regional geology and hydrogeology The soil samples and drill <br /> cuttings from MW8 indicated similar lithologies to those <br /> presented in the Problem Assessment Report <br /> HYDROLOGY <br /> Ground water elevations at the site ranged between 5 and 6 feet <br /> below sea level from January 20 , 1989 to April 18 , 1989 From <br /> April 18 , 1989 through September 13 , 1991, ground water <br /> elevations decreased an average of eight feet, to approximately <br /> 13 feet to 14 feet below sea level This decrease may be <br /> attributed to both sampling time (summer vs winter) as well as <br /> an effect of the continuing drought period <br /> 2 <br />