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S E C 0 R QUARTERLY SUMMARY REPORT FOURTH QUARTER 2003 ConocoPhdlips (former BP) Service Station #11193 3202 West Hammer Lane, Stockton California City/County ID # Stockton County San Joaquin BACKGROUND The site is located at 3202 West Hammer Lane in Stockton, California, and is an operating 76 service station The site currently contains three gasoline USTs, associated product Imes, and dispenser In April 1987, KEI observed the removal of one 1,000-gallon waste oil tank on the southwestern portion of the site One soil sample was collected from the base of the excavation at approximately 10 feet below ground surface (bgs) Laboratory analytical results detected gravimetric waste oil as petroleum oil at 55 parts per million (ppm)(EMCON, 1994) Between December 3, 4 and 10, 1992, RESNA performed a preliminary site assessment for British Petroleum (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, respectively, of the underground storage tanks (USTs),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- 02), and total xylenes at 0 0240 ppm (S-21 3-132) 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 of 1994, 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 on the northeast corner of the property, Well MW- 6 was installed in an alley west of Kelly Drive, and MW-7 was installed on the north side of West dm Hammer Lane Laboratory analysis+ it samples detected maximum concentrations of benzene at 0 13 ppm (MW-5-16'), toluene at 9W7 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 consisting of collecting two grab sod samples (TD-2 and TD-3) below the eastern fuel dispensers at the north and south dispensers, drilling of two sod 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 sod 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 (TPH-O), 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 n