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Mr. J. Kelly Williamson <br /> Kayo Oil Company <br /> April 8, 1985 <br /> Page 2 <br /> both borings. A faint old petroleum odor was noted at a depth of <br /> 25 feet in MW-7, with a 2 percent LEL reading. The soil sample <br /> collected in MW-5 at a depth of 15 feet was analyzed by IT Stoner <br /> Analytical Laboratories using the EPA 602 method. Laboratory results <br /> are shown on Table 1. <br /> The soil profiles were characterized by silty sand (SM) with gravel near <br /> the surface. MW-5 and MW-6 encountered occasional sandy silt (ML) <br /> interbeds. Clayey sand (SC) was encountered at a depth of 17.5 to <br /> 27 feet in MW-7. <br /> Conclusions and Recommendations <br /> Monitor wells MW-3, MW-4, and MW-5, which are located adjacent to or <br /> within 8 feet of the tanks, detected hydrocarbons. In all three bor- <br /> ings, the highest LEL reading was at a depth of 15 feet, with a signifi- <br /> cant decline in values with depth. Monitor wells MW-1, MW-2, and MW-6, <br /> which are located 14 feet, 13 feet, and 20 feet out from the tank farm, <br /> respectively, did not detect an LEL reading over 4 percent. This would <br /> indicate that hydrocarbons at a significant level are restricted to the <br /> tank backfill . <br /> We recommend that the wells be monitored for hydrocarbon vapors. If the <br /> tanks are replaced, removal and disposal of the tank backfill as a haz- <br /> ardous waste will be required. Some overexcavation to remove contami- <br /> nation immediately adjacent to the backfill may also be desirable. <br /> We trust the information contained herein meets your needs at this <br /> time. If you have any questions concerning this work, please feel free <br /> to contact me at our Martinez, California office (415) 228-8400. <br /> Very truly yours, <br /> D <br /> Thomas C. Shoff <br /> Prot Manager <br /> Robert M. Galbraith, R.G. 3881 <br /> Manager, Geotechnical Services <br /> RMG:jc <br /> 0025 <br />