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4.1.2 Soil Borings To evaluate and delineate residual hydrocarbons in the soil, a total of 24 soil borings (B-1 through B-24) were drilled at the site (RESNA, April 7, 1992, Report No 38048-5, RESNA, January 7, 1993, Report No 38048-7, and RESNA, June 8, 1994, ' Report No 38048-11) The locations of the borings are shown on Figure 2 Details of the borings, such as boring depth, diameter, and drilling methods, are summarized in Table 2 During drilling, geologists collected soil samples at approximately 5-foot intervals Samples were identified using visual and manual methods and classified using the Unified Soil Classification System Descriptions of the materials encountered are presented in the logs of borings (see Appendix B) During sampling, a photoionization detector (PID) was used to characterize the relative levels of hydrocarbon vapors emitted by the soil samples PID readings recorded in the field are reported in parts per million by volume (ppmv) and ' are shown on the logs of borings ' 4.1 3 Disposal of Excavated Soil The soil excavated from the former gasoline cavities, new tank cavity, product line trenches, and waste-oil tanks was stockpiled on site, placed on and covered with plastic sheeting RESNA collected and analyzed soil samples from the stockpiled soli to evaluate disposal options At the request of the SJCPHS, ARCO submitted a letter to the SJCPHS requesting authorization to backfill the former tank cavity with approximately 250 cubic yards (cy) of the stockpiled soil Authorization was granted verbally from the SJCPHS on July 17, 1991 (RESNA, April 7, 1992, Report No 38048-5) After obtaining analytical results of composite soil samples and at ARCO's request, approximately 150 cy of soil that was below laboratory detection hiruts for residual hydrocarbons was transported to private land at the corner of Hibbard and Tokay Colony Road in Lodi, Cahfomia, to be used as backfill material The soil generated from the waste-oil tank cavity (approximately 150 cy) was transported to the Browning Ferns Industries, Inc , (BFI) Class II landfill in ' Livermore, California ' 4 1.4 Vapor Extraction Well Construction From June 1991 to January 1994, RESNA constructed vapor extraction wells VW-1 through VW-11 in bonngs B-9 through B-15, B-17, B-18, B-20, and B-24 The vapor extra(.tion wells were installed to be used during a soil vapor extraction (SVE) test to evaluate the feasibility of remediating petroleum hydrocarbons in the soil using an SVE system Well construction details are presented in Table 3, and the construction details of the individual wells are depicted on the logs of borings (see Appendix B) SA(1N\PJ0\OS0W805i4204BS 97yirt I Rev 0 3112197 20805 142 004 4-2