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. Closure Report - Chevron Station#9-1848 Jmuary 18, 1999 �► GSI witnessed the removal of one 5,000-gallon and two 10,000-gallon gasoline underground storage tanks(USTs)and associated product lines, a 1,000-gallon waste-oil UST, four hydraulic hoists and 15-gallon hydraulic fluid tank, a grease trap, and an oil- water separator Soil samples were collected beneath all subsurface facilities removed Five soil samples were also coIIected from the base of the new gasoline UST pit Total Petroleum Hydiocarbons as gasoline (TPHg) and benzene were detected in all six of the soil samples collected at approximately 16 feet bgs from the former gasoline UST excavation TPHg and benzene were also detected in the product line soil samples collected from a depth of 4 5 feet bgs Five soil samples collected at a depth of 1S feet bgs from the new gasoline UST excavation contained detectable TPHg and benzene concentrations The soil sample with the highest concentration of TPHg (2,100 ppm) wag collected from the southern product line trench at a depth of 4 5 feet bgs The highest benzene concentiation (2 4 ppm) was detected in the soil sample collected at depth of 16 feet bgs beneath the southern end of the 5,000-gallon gasoline UST Low concentrations of TPHg were detected in the two soil samples from the waste oil UST pit, and benzene was detected in one of these samples Total Petroleum Hydrocarbons as oil (TPHo) were not detected in any of the soil samples except for one collected from the westein hydraulic lift Data from this investigation are presented in GSI's Tank Replacement Observation Report, dated August 23, 1991 Soil Chemical Analytical data are included in Appendix A-1, and Soil sample locations are shown on Figures 3 e To evaluate the extent of hydiocaibon impact to soil and groundwatet beneath the site, thiee gioundwater monitoiing wells (C-1 through C-3) were installed by GSI on July 23, 1991 Eight soil samples were submitted for analysis of TPHg and benzene, toluene, ethylbenzene, and total xylenes (BTEX) The soil samples collected from well boring C-2, located in the vicinity of the former waste-oil UST, were also analyzed for TPHd and TPHo Six of the eight soil samples did not contain detectable TPHg or benzene concentrations TPHd or TPHo were not detected in any of the soil samples analyzed However, TPHg were detected in two samples collected at depths of 19 5 feet (well boring C-1) and 16 feet (well boring C-2) bgs at concentrationg of 2 0 and 13 ppm, respectively Data from this investigation are presented in GSI's Well Installation Report, dated September 5, 1991 Soil chemical analytical data are presented in Appendix A-2, and well boring Iocations are shown on Figure 3 ® To further define soil and groundwater conditions beneath the site, GR advanced four exploratory soil borings on August 23, 1997 The four borings were advanced to a 340392 02 cl 2 I