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Clayton 10 INTRODUCTION Orchard Supply Hardware retained Clavton Environmental Consultants, Inc to conduct a limited shallow soil boring program We conducted this program to define the hoiizontal and vertical extent of'otal recoverable hydrocarbons idem,fed in the sails on the Orchard Supply property at the corner of MacArthur Drive and Grant Line Road in Tracy, California In addition, Clayton was retained to locate and properly abandon a second septic tank onsite Clayton had previously abandoned a septic tank on August 17, 1590 (Figures 1 and 2) Mr. Michael D LaTourette, Diiector of Real Estate, authorized this project on March 29, 1991, by accepting Clayton's Proposal No 91-13-045 and its accompanying tarms and conditions Clayton commenced field work on April 5, 1991, after obtaining a permit to install the boreholes from the San Joaquin County Public Health Services (Figure 2; A copy of the permit application is provided in Appendix A C!ayton also obtained a permit for septic tank destruction from San Joaquin County Public Health Services, and on April 25, 1991, performed field work that confirmed the proper destruction of septic tank #2 (Figure 2). A copy of the permit application is provided in Appendix D In addition, Clayton conducted a quarterly water sampling of monitoring well MW-3B on May 2, 1991. 20 On January 8, 1991, Clayton installed a new monitoring we11 downgradient of the former underground storage tank excavation to replace the monitoring well destroyed during recent excavation (Clayton Project No 32649, dated February 11, 1991) We sampled all three existing wells In soil samples collected from 4 feet below ground surface during construction of the new monitoring well, MW-3B, we detected 770 t milligrams per kilogram (mg/kg) total recoverable hydrocarbons Based on these findings, Clayton recommended a limited shallow soil boring program to define the horizontal and vertical extent of soil contamination. 30 FIELD MDMSIMATM Installation and sampling of five boreholes (BH-1, BH-2, BH-3, BH-4, and BH-5) and quarterly water samphng of tnonitoring well MW-113 was performed in accordance with Claytods drilling, well construction, and sanipltng protocols {Appendix B) The borehole installation was observed by Ms Diane M Hinson, San Joaquin County Public Health Services, Supervising Environmental Health Inspector. Mr Gregory Olivera, San Joaquin County Public Health Services, Environmental Health Specialist, was present to observe field work for destruction of the septic tank -1- i