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lbBack round <br /> The site consists of three 12 , 000 gallon steel underground <br /> storage tanks Presently, the tanks store regular unleaded, <br /> super unleaded, and premium unleaded gasoline. USA records <br /> indicate no significant loss or gain in the inventory. The site <br /> has three service islands, each with a vapor recovery system. <br /> USA Petroleum has acquired 9 monitor wells in the course of the <br /> investigation of this site . Five of these wells are located <br /> within USA property and four wells are to the south in a <br /> downgradient dzrecelon (see Figure 3) . After the existing wells <br /> were in place, a Problem Assessment Report was prepared December <br /> 5, 1989 This report is included in Appendix A of the Quarterly <br /> Monitoring Report of September 24, 1991 It presents Soil Boring <br /> analysis, Ground water analysis, Ground water flow direction, <br /> Aquifer test data with an estimate of tranpmissivity and <br /> hydraulic conductivity, and an evaluation of the zero line of <br /> contamination <br /> GeGeo�Y <br /> The deposits under the site are Recent to Pleistocene age <br /> alluvium and consists 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 <br /> HYDROLOGY <br /> The ground water had maintained an elevation of between 5 and 6 <br /> feet below sea level from January 20, 1989 to April 18, 1989 <br /> during a period of ground water elevation measurements following <br /> the installation of MW4, MWS, MW6 and MW7 from January to March, <br /> 1985. From April 18, 1991 through September 13, 1991, ground <br /> water elevation at the site decreased to approximately 13' to 14' <br /> below sea level This may be attributed to both sampling time <br /> (summer vs . winter) as well as an effect of the continuing <br /> drought period Since the last sampling round in June of 1992, <br /> there has been an over all increase of approximately 1, in the <br /> ground water level at this site (see Table 1) . The present <br /> ground water flow direction, Figure 4D, is south to southeast <br /> The hydraulic gradient is fairly flat across the site from MWi to <br /> MW7 at a slope of . 0038 . <br /> i 2 <br />