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S ECOR 76 Station No. 11193 August 13, 2004 Page 2 k results reported gravimetric waste oil as petroleum oil at 55 parts per million (ppm, EMCON, 1994). Between December 3 and 10, 1992, RESNA performed a preliminary site assessment for BP by drilling four exploratory soil borings (B-1 through B-4) to total depths of 31.5 to 36.5 feet bgs and converting them to Groundwater Monitoring Wells MW-1 through MW-4. Wells MW-1 and MW-2 were installed on the southeast and northwest corners of the USTs, respectively. Well MW-3 was installed on the west end of the northern dispenser island and Well MW-4 was installed between the former waste oil tank and the new waste oil tank. Laboratory analytical results for soil detected maximum concentrations of benzene at 0.1200 ppm (S-21.3-B2), toluene at 0.0200 ppm (S-20.0-B1), ethylbenzene at 0.0180 ppm (S-21.3-B2), and total xylenes at 0.0240 ppm (S-21.3-B2). Gasoline range total petroleum hydrocarbons (TPHg) and diesel range total petroleum hydrocarbons (TPHd) were not"detected above laboratory detection limits. Laboratory analytical results for groundwater detected maximum concentrations of TPHg at 2,200 parts per billion (ppb, MW-1), benzene at 120 ppb (MW-2), toluene at 15 ppb (MW-1), ethylbenzene at 1.0 ppb (MW-2), and total xylenes at 24 ppb (MW-2). TPHd was not detected above laboratory detection limits (RESNA, 1993). In March 1994, Alisto Engineering (Alisto) conducted a supplemental subsurface investigation by drilling and installing three groundwater monitoring wells (MW-5 through �• MW-7) to total depths of 31 to 32 feet bgs. Groundwater Monitoring Well MW-5 was installed in the northeast point of the property, Well MW-6 was installed in an alley east of Kelly Drive, and MW-7 was installed on the north side of West Hammer Lane. Laboratory analysis of soil samples detected maximum concentrations of benzene at 0.13 ppm (MW- 5-16'), toluene at 0.67 ppm (MW-6-16'), and total xylenes at 0.015 ppm (MW-5-16'). TPHg and TPHd were not detected above laboratory detection limits (EMCON, 1994). On November 22, 1994, EMCON conducted a supplemental site assessment to establish baseline subsurface conditions during the transfer of ownership of the property from BP to Tosco. The investigation consisted of collecting two grab soil samples (TD-2 and TD-3) below the north and south dispensers, drilling of two soil borings (THP-1, THP-2) to total depths of 26.5 feet bgs, and the drilling and installation of vapor extraction well VW-1 to a total depth of 17 feet bgs. Soil and HydroPunch® groundwater samples were collected and analyzed from borings THP-1 and THP-2. Laboratory analysis of soil samples TD-2 and TD-3 detected maximum concentrations of TPHg at 2,100 ppm (TD-2), toluene at 3.5 ppm (TD=3), ethylbenzene at 18 ppm (TD-3), and total xylenes at 110 ppm (TD-3). TPHd, oil range total petroleum hydrocarbons (TPHo), and benzene were not detected above laboratory detection limits. Laboratory analysis of soil samples from borings THP-1 and THP-2 detected maximum concentrations of TPHd at 1 ppm (THP1S-10) and benzene at 0.03 ppm (THP@S-15). TPHg, TPHo, toluene, ethylbenzene, and total xylenes were not detected.above laboratory detection limits. Laboratory analysis of groundwater samples from borings THP-1 and THP-2 detected maximum concentrations of TPHg at 6,900 ppb (THP2W-21), TPHd at 840 ppb (THP2W-21), benzene at 1,900 ppb (THP2W-21), and total xylenes at 77 ppb (THP2W-21). TPHo, benzene toluene, ethylbenzene, and Halogenated .� Volatile Organic Compounds (HVOC's) were not detected above laboratory detection limits (EMCON, 1994). i i I:1ConocoPhillips\Tosco Marketing1111931Reports\ozone Well instali Rpt 6-04 recovered.doc