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ERI 205503 1101 Unocal Service Station 5886 Stockton California June 3 1997 <br /> 3.0 PRESENT INVESTIGATION <br /> 3.1 Fuel System Inte rit <br /> In response to concerns raised by the San Joaquin Public Health Department related to the detection <br /> of MTBE in groundwater during successive quarters, 76 Products Company (now Tosco) requested an <br /> inspection of the site for fuel leaks On March 20, 1997, Banks and Company (Banks) of Fresno, <br /> California performed an inspection The inspection did not note any leaks in the existing piping or in <br /> UST interstitial spaces The Inspection report is attached (Appendix A) <br /> ERI also contacted Sequoia Analytical Laboratory to obtain methyl tert-butyl ether (MTBE) results of <br /> previous water samples collected from geoprobes Sequoia has been unable to locate the <br /> chromatograms to date <br /> 332 Scoj2e of Work <br /> ERI performed the field work in accordance with ERI's Work Plan (dated March 27, 1997) and <br /> Addendum to Work Plan (dated April 3, 1997) and approved by San Joaquin County Public Health <br /> Services (SJCPHS) Environmental Health Division on April 10, 1997 ERI obtained a permit to drill <br /> the soil borings from the SJCPHS before beginning work (Appendix B) ERI performed field work at <br /> the site in accordance with a Site Safety Plan which was kept on site during field operations ERI S <br /> standard field protocol is included In Appendix C <br /> 333 Soil Borings <br /> j On April 15, 1997, an ERI representative hand augured three soil borings (HAI through HA3) In the <br /> vicinity of select catch basins located adjacent to dispenser islands to a depth of approximately 2 5 to <br /> 3 feet bgs and collected soil samples Mr Ron Rowe of SJCPHS authorized boring locations and <br /> observed hand augering and sampling ERI also observed Woodward Drilling, Inc (Woodward) of <br /> Rio Vista, California, drill four on-site soil borings (134 through 137) and construct duel completion <br /> monitoring wells MW4S through MW7S and MW4D through MW7D in these borings Drilling was <br /> 3 <br />