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S F C 0 R 7-Eleven Store Number 14117 Fuel Line Upgrade Soil Sampling Report July 31, 2003 Page 2 On September 29 and October 2, 1998, Fluor-Daniel GTI advanced six offslte (OSGP-1 through OSGP-6) and 11 onsite (GP-7 through GP-17) Geoprobe soil borings The offsite borings did not contain total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, and total xylenes (BTEX), or methyl-tert-butyl ether(MtBE) in soil above laboratory reporting limits The onsite borings reported benzene, TPHg, and MtBE at maximum concentrations of 12 5 milligrams per kilogram (mglkg) (GP-17@20'), 42,900 mg/kg (GP-15@15'), and 234 mg/kg (GP-14@10'), respectively (Fluor Daniel GTI, 1998) On May 13 and 14, 1999, four groundwater monitoring wells (MW-1 through MW-4) were advanced to 51 feet below ground surface (bgs) Benzene, TPHg, and MtBE in soil were reported at maximum concentrations of 2 89 mg/kg (MW-3-15'), 429 mg/kg (MW-3-15'), and 0 119 mg/kg (MW-4-20'), respectively (1T Corporation, 1999) On October 30, 2001, three groundwater monitoring wells (MW-5, MW-6, and MW-7)were advanced to 20 feet bgs TPHg, BTEX, and MtBE in soil were not detected above laboratory reporting limits, except for 0 006 mg/kg total xylenes (MW-7@20') Selected halocarbons also reported in the soil samples indicated possible dry cleaner plume contributions (IT Corporation, 1999) An active USA Gasoline (former Exxon) service station is located east of the site Previous figures and tables are included in Attachment A SITE LOCATION AND FACILITY DESCRIPTION E The site is an active service station located in a mixed residential and commercial area along Country Club Boulevard in Stockton, California (Figure 2) The site is occupied by an operating 7- Eleven convenience store with two USTs and two dispensers The dispenser islands and UST areas are paved with concrete and the remainder of the site is surfaced with asphalt FIELD ACTIVITIES Dispenser Sample Collection and Analyses On April 21, 2003, SECOR's field technician collected a total of four soil samples from native soil, two from beneath the fuel dispensers and two along the product lines All samples were collected under the direction of a SJCEHD representative Each soil sample was screened for hydrocarbon vapors using a portable photoionization detector (PID) Soil samples were collected in clean, 2-inch diameter by 6-inch-long brass sample tubes A SECOR scientist used a hand auger to extract soil I then, pounded a sample tube into the soil in the center of the auger The sample tube was filled completely with soil to minimize headspace and sealed using Teflon® sheeting and plastic end caps Each soil sample was labeled and placed in a cooler on ice for delivery to Kiff Analytical in Davis, California All soil sampling equipment was cleaned with a non-phosphate detergent solution and rinsed with tap water followed by a distilled water rinse to reduce the possibility of cross- contamination between sample locations Copies of the field notes are included in Attachment B and the soil sample locations are shown on Figure 2 . The soil samples were analyzed for TPHg, BTEX, MtBE, di-isopropyl ether (DIPS), tert-amyl-methyl ether (TAME), ethyl-t-butyl ether (ETBE), and tert-butyl alcohol (TBA) using EPA Method 8260B Soil samples were also analyzed for total lead using EPA Method 6010E ECOR International Inca orated File 7-Eleven/Store 20220/Reports/14117 Fuel Line Upgrade Report doc S rA