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09 August 1999 AGE-NC Project No. 98-0466 ' Page 3 of 10 t . • Advancement of two soil borings,fo 50'feet bsg' the former dispenser-area excavation and in the former UST pit to collect•soil and ground water samples; Obtaining laboratory analysis of the ground wat r samples and selected soil samples; and • . Preparation of a site assessment report or a-clos a summary report, as appropriate,based on.. the results of the investigation. A'site plan showing structures and boring locations on the subject property is shown on Figure 2: This closure summary reporthas'been prepared in acco dance with PHS-EHD and Central.Valley Regional Water Quality Control"Board'(CVRWQCB) guidelines. 2.0. -BACKGROUND ` A. 10;000-gallon, steel underground-storage.tank (UST).was utilized for diesel fuel on the site as early as.1983. The UST'system failed a precision test on 18 November 1988 and a product line was r^ repaired on 15 December 1988. . r" 2.1. UST REMOVAL The UST was removed under inspection by the PHS-E D on 27 August 1993. Two soil samples were collected from beneath the former UST location and two samples were collected from beneath the product line piping: The samples collected under the north end of the UST and the north end of the product line..contained.less .than detectable concentrations of total petroleum hydrocarbons quantified as gasoline (TPH-g), total petroleum hydrocarbons quantified as diesel (TPH-d), and benzene,toluene, ethylbenzene and xylenes (BTEX}. TPH-g and TPH4 were detected in the south r., UST sample at concentrations of 5.5 milligrams per kilogram (mg/kg) and 63 mg/kg; and in the . south product line piping sample at concentrations of 89 mg/kg and 910 mg/kg,-respectively. A :,piping stockpile soil sample contained 450 mg/kg PH-g and 5,800 .mg/kg TPH4 Minor concentrations of.toluene, ethylbenzene.and xylenes w re detected in some samples; benzene was not detected ir[any samples. The analytical results of the soil samples are included in Table 1. 2.2, SITE REMEDIATION Excavation was initiated on the site withouta site assessment having been performed. A letter work Plan for excavation of impacted soil was prepared by Stockton Service .Station Equipment Co., Inc. (SSSEC) on 27 January.1994 and amended by an add ndum dated, 02 March 1994. The area of Advauced GeoEnvironmental,Inc.