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. � <br /> Ms.Lori Duncan <br /> M1 = June 12,2007 <br /> COMSTOGA-ROVERS <br /> &ASSOCIATES <br /> SITE DESCRIPTION AND BACKGROUND _ <br /> The site is an operating Shell-branded service station located on the northwest corner of West Grant Line <br /> 'Road and Joe Pombo Parkway in Tracy, California(Figure l): The site layout(Figure 2) consists of four <br /> underground storage tanks (USTs), .nine dispenser islands containing eleven dispensers, a station <br /> _ building, and a car wash. There are three active service stations:located nearby the subject site. An <br /> ARCO service station is located to the cast, 'a 7-Eleven service station is located.to the south, and,.-a <br /> Valero service station is located to the,southwest of the subject site... <br /> The 7-Eleven site is an active environmental case overseen:by the San Joaquin County Environmental <br /> Health Services (SJCEHD). A site investigation 'report,for the 7-Eleven site issued'by SECOR <br /> International, Inc. (SECOR) on September 30, 2004 stated that methyl tertiary butyl ether(MTBE) from <br /> the 7-Eleven.site has migrated to-the north and northwest,beneath the Shell site.' . <br /> SITE GEOLOGY. <br /> The .predominant soil type beneath'the site is fine-grained soils '(silts and clays) to'the total depth„ <br /> explored of approximately 86 fbg. Silty sand and sand layers have been encountered that do not appear <br />;- to be laterally continuous across the site. .A site cross section is presented as Figure 3.-. <br /> HYDROGEOLOGY _ ~ <br /> Since 2003, depth to water beneath the subject site has ranged from 9.6 to 13.5 fbg in the monitoring <br /> wells, and groundwater elevations have ranged from 11.4'to 16.2 feet above mean sea level. Table I <br /> : . presents well construction details. The groundwater flow�direction is typically toward.the north or <br /> northwest with the groundwater gradient varying from 0.02 to 0.007. <br /> SENSITIVE RECEPTORS.. <br /> Cambria performed a sensitive receptor survey to update the previous receptor survey and'ideritify water <br /> production wells and surface water bodies within a 2,000-foot radius of the site.,,Figure I shows the area <br /> encompassed by the sensitive receptor survey. <br /> Water Well Survey: Cambria reviewed the Department of Water Resources' (DWR's) records the State <br /> Water Resources Control;Board Geotracker database (Geotracker) for water-producing wells within a <br /> 2,000-foot radius of the site." Geotracker,did not list any public water wells within one mile of the site.. <br /> ]667 _ 2 <br /> ' Worldwide Engineering, Environmental,Construction,and IT Services <br />