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S E C 0 R IConceptual Site Model . Chevron Service Station #9-6171 March 25, 2005 Page 6 Subsurface Investigation Report— 1992 On July 30, 1992, SES Installed one on-site monitoring well (MW-6) Soil samples from 16 feet and 56 feet bgs were analyzed for TPHg by EPA Method 8015/5030 and BTEX by EPA Method 8020 BTEX compounds were not detected in the soil samples In addition, there were no gasoline or diesel range petroleum hydrocarbons detected in the soil samples On July 31, 1992, monitoring well MW-1 was abandoned due to a lack of water The casing of MWA was drilled out and the soil boring was grouted to the surface with a mixture of Portland cement and 3 to 5% bentonite Installation of Monitoring Well MW—7 No Information Is available on the Installation of monitoring well MW-7 MW-7 has been sampled quarterly starting September 15, 1993 It Is assumed that MW-7 was Installed Ibetween July 30, 1992 and September 15, 1993 Soil Borings— 1995 IPacific Environmental Group, Incorporated (PEG) drilled five soil borings (B-1 through B-5) on September 22, 1995 in the vicinity of the current USTs and former product islands (Figure 2) Boring B-3 was not completed due to drilling refusal at 4 feet caused by a metallic object Two additional boring locations near B-3 were attempted but were also terminated at 4 feet due to drilling refusal However, samples collected within the 4 foot Interval were sent to the laboratory for analysis Samples submitted for analysis were analyzed for TPHg by EPA Method 8015 and for BTEX by EPA Method 8020 Samples from borings B-1, B-2, and B-4 did not have detectable amounts of TPHg, benzene, toluene, ethylbenzene and xylene The sample collected from 2 ft bgs was submitted for analysis from boring B-3 and contained 56 mg/kg TPHg, 0 042 mg/kg toluene, 0 17 mg/kg ethylbenzene and 16 mg/kg xylene The sample collected from 10 ft bgs was submitted for analysis from boring B-5 and contained 0 013 mg/kg toluene and 0 031 mg/kg total xylenes Underground Storage Tank and Piping Removal - 1997 From December 1997 to January 1998, three hoists, two waste oil storage tanks, and the associated product piping were removed during a station renovation At this time, WOT-1 (1,000-gallon capacity) was removed A previously unknown waste oil tank (WOT-2) and a 6-inch steel well (OW-1) were discovered immediately south of the northeast canopy footing Soil and groundwater samples were submitted for analysis by EPA Methods 8015, N 1FAesIProjectslchevronlRetadl#9-61711Site conceptual ModelTINAL_CSM doo