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QRION <br /> 1 .0 INTRODUCTION <br /> r <br /> Bridgestone/Firestone, Inc. (BFS) has retained Orion Environmental Inc. (Orion) to conduct <br /># groundwater assessment:activities at the former BFS facility at 400 North EI Dorado Street <br /> in Stockton, California (the site; Figure 1). This document summarizes the work planned <br /> to delineate the nature and extent of impacted groundwater at the site and has been <br /> prepared in response to a letter from the San Joaquin County Environmental Health <br /> Division (SJCEHD) dated 30 August 1999. <br /> 1.1 Background <br /> The site is the former location of an automobile gasoline station that operated during the <br /> 1920s and 1930s. After this. period the site was used as a retail tire and automobile <br /> I service center. In 1967, four undergroundstorage tanks (USTs} were closed in place by <br /> filling the tanks with sand. I.n 1991, one -of these .previously closed tanks was removed i <br /> from.the site along with eleven other USTs previously located at the site. The size of the <br /> remaining tanks are. reported as follows; Tanks 1 and 3 are 7,500 gallon capacity and <br /> 3 Tank 2 is 550 gallons. <br /> In May 1997, four slant borings were drilled in the vicinity of the three remaining USTs <br /> by Foothill Engineering. Total petroleum hydrocarbons as gasoline (TPHg) were detected <br /> in soil samples beneath tank#3 at concentrations up to 16,200 milligrams per kilogram <br /> (mg/kg). No groundwater samples were collected during this investigation. <br /> �? In December 1998, soil borings BFS-1 and BFS-2 were drilled in the vicinity of the three <br /> closed-in-place USTs by QST Environmental (QST). Figure 2 shows the boring locations. <br /> M Groundwater was encountered in these borings at approximately 28 feet below grade. <br /> Groundwater from boring - BFS-1 contained detected concentrations of TPHg of <br /> �+ 4,200 micrograms per liter (I.g/I) and benzene, toluene, ethylbenzene, and xylenes (BTEX) <br /> of 220 I, 400 1, 340Vg/l,-and 1,500 1, respectively. MTBE was also detected in <br /> µ� µ� _ µ� P Y• <br /> groundwater from boring BFS-1 at.a concentration of 0.78 µg/l. Of the gasoline-related <br /> compounds listed above, only xylenes were detected in. a groundwater sample obtained <br /> l from boring BFS-2 (0.55 4g/1). <br /> SNBF5\ST0CKT0N\WKP001.D0C 10/27/99 1-1 <br />