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I <br /> Final Remedial Plan 2 September 1992 <br /> 3788 Tracy Boulevard Rev. : D1 <br />' Tracy, California P1745R005.WP <br /> at one location in the center. As this sand was not observed <br />' elsewhere, it is probably discontinuous. Logs showing soil <br /> materials encountered during drilling are attached as Appendix A. <br />' In addition to the natural l -occurring sediments the <br /> Y g <br />' property is overlain by an imported sand layer as much as three <br /> feet thick which raises and levels the pad below the asphalt top. <br />' The measured depth to groundwater has averaged nine feet <br /> during the year the onsite wells have been monitored. Groundwater <br />' flow direction has been to the north-northwest, with a gradient of <br /> approximately 0. 002 foot per foot. Table 1 lists measured depths <br />' to groundwater during the year the wells have been monitored. <br /> AREAS IDENTIFIED FOR TREATMENT <br />' Following removal of the underground waste-oil storage <br /> tank in June 1990, oil-contaminated soil was removed, leaving a 9' <br />' by 12' by 14. 5' deep pit which was backfilled with clean gravel. <br /> Not all oil-contaminated soil was removed due to the proximity of <br />' the gasoline USTs. <br /> Laboratory analysis of soil samples taken from the base <br /> of the over-excavated tank pit indicated 3 .7 parts per million <br /> (ppm) Total Extractable Petroleum Hydrocarbon (TEPH) at the 14' <br /> Idepth. The same soil samples were analyzed for the compounds <br /> benzene, toluene, ethylbenzene, and xylenes (BTEX) and none was <br /> present in excess of the detection limit of 0. 005 ppm. Three <br /> sidewall samples, collected 5" to 12" above the observed water <br /> level, had TEPH of 210 ppm (north wall) ; 95 ppm (north side of the <br /> east wall) ; and 270 ppm (south side of the east wall) . All samples <br /> were analyzed for halogenated volatile organic substances and for <br />