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J <br /> locations, the concentration of TPHG left in place was 1 ,300 mg/kg in <br /> boring B-1 (near the northwest corner) at a depth of 31 feet, 338 mg/kg in <br /> the confirmation sample at the north-central side of the excavation at a <br /> depth of 32 feet, and 2 mg/kg in the confirmation sample at the bottom <br /> center of the excavation at a depth of 38 feet. Benzene was left in place at <br /> two locations. At these locations, the concentration of benzene left in place <br />' was 8.2 mg/kg in boring B-1 at a depth of 31 feet and 0.037 mg/kg in the <br /> confirmation sample at a depth of 38 feet. <br />' f Also, in September 1987, wells MW-4 and MW-5 were installed to assess <br /> impact to ground water, if any, resulting from the release. Section 2.4 pre- <br /> sents additional information on completed ground-water characterization <br />' activities. <br /> 2.2 Removal of Tank C-12 <br /> Tank C-12, a 10,000-gallon-capacity regular gasoline storage tank, was <br /> removed in August 1988 (see Drawing 1). Two soil samples were <br /> col-lected from the tank excavation for chemical analysis. One of the samples <br /> contained detectable concentrations of benzene, toluene, ethylbenzene, <br /> ' and xylenes (BTEX). BTEX was not detected in the other sample, and <br /> TPHG was not detected in either sample. In September 1988, the area <br /> was overexcavated. Confirmation soil samples were collected from the <br />' bottom of the excavation. Soil sample analytical results are presented in <br /> Table 3 and on Figures 2 and 3. Petroleum hydrocarbons were not <br /> detected in any of the confirmation soil samples collected from this <br />' overexcavation activity. <br />' 2.3 Removal of Tanks IE and t° <br /> In March 1991 , tank E (550-gallon-capacity tank) and tank F (1 ,000-gallon- <br /> capacity tank) were removed from the site (see Drawing 1). In March <br /> 1990, prior to the removal of these tanks, an exploratory soil boring (BH-1) <br /> was drilled adjacent to tank E, and three soil samples were collected for <br /> chemical analysis. None of the samples contained detectable <br /> concentrations of TPHG. However, the sample which was collected at <br /> 10 feet was analyzed for total petroleum hydrocarbons as diesel (TPHD), <br /> and contained 2,900 mg/kg of this compound. <br /> During the removal of tank E, one soil sample was collected from the bot- <br /> tom of the excavation and analyzed for TPHG, BTEX, ethylene dibromide, <br /> p#\f921f920201 a 3 Rev. 0 June 1, 1992 <br /> - - Er:C011 2820 WO4 q <br />