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i <br /> i <br /> 1 .0 INTRODUCTION/PREVIOUS WORK <br /> Th: j report is being submitted in response to a request by <br /> the San Joaquin County Public Health Services, Environmental <br /> Health Divisionision for a site investigation at the Western <br /> Stene Products facility, 8181 W. 11th Street, Tracy. <br /> On August 23, 1988, three underground fuel storage tanks <br /> were removed from the project site. The number, capacities <br /> and contents of the tanks were as follows: 1) One 2,000 <br /> gallon unleaded gasoline; 2 ) One 380 gallon regular <br /> gasoline; and 3) One 1,000 gallon diesel. California Water <br /> Labs collected soil and groundwater samples from beneath the <br /> fuel tanks. Analytical results for the samples are <br /> summarized on Tables 1 and 2. Due to the presence of <br /> elevated concentrations of petroleum hydrocarbons in the <br /> groundwater sample, further assessment was required. <br /> 2.0 INVESTIGATION PROCEDURE <br /> 2.1 Soil Barings <br /> �.a On October 23 and 24, 1989, three soil borings were <br /> advanced to depths ranging from 21 to 25 feet below grade <br /> for the dual purpose of site soil characterization and <br /> r groundwater monitoring well installation ( Figure 2) . <br /> Drilling was conducted by Osterberg and Stewart (C57 license <br /> # 446670) using an Ingersol/TH-10 rig with 10-inch (O.D. ) � <br /> hollow stem augers. During drilling, soil cuttings were <br /> logged continuously by a field geologist utilizing the <br /> Unified Soil Classification System (Appendix I ) . <br /> Descriptions of soils encountered in the boreholes are <br /> recorded on the well logs (Appendix I ) . <br /> Soil samples were collected at 8.5 feet, near the top of the <br /> capillary fringe in each borehole. Sequoia Analytical, a <br /> state certified lab, analyzed the samples for benzene, <br /> toluene, ethylbenzene, xylenes (BTEX) and total petroleum <br /> hydrocarbons (TPH) as diesel by EPA methods 8020/8015. <br /> 2. 2 Monitoring/Vapor Extraction Wells <br /> The three soil borings were completed as two inch diameter <br /> monitoring wells. Specific details of the well <br /> completion/construction are included on the boring logs <br /> (Appendix I) . After completion, the depth to groundwater in <br /> the monitoring wells were measured using a conductivity <br /> probe. <br /> �-* The three monitoring wells were developed by pumping at a <br /> rate of 1 .4 gallons per minute (gpm) for a period of 45 <br /> minutes in order, to remove at least four well volumes <br /> (casing plus sandpack) . Groundwater samples were collected <br /> using a teflon bailer with a bottom emptying device. The <br />