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S E C O R - - 7-Eleven Store Number 20632 . Fuel Line Upgrade Soil Sampling Report December 15, 2003 Page 2 Additional lateral and vertical assessment of dissolved methyl-tert-butyl ether (MtBE) and other petroleum hydrocarbons has been conducted A total of seven onsite groundwater monitoring wells are used to monitor groundwater conditions at the site In April 2002, three onsite monitoring wells (MW-4R, MW-6, and MW-7), two dual-nested sparge/vent wells (SPV-1 and SPV-2) and a vertical delineation soil boring (SB-1) were installed at the site On April 22, 2002, a soil vapor extraction (SVE) test was performed at the site Vapor was extracted from MW-4R, MW-7, SPV-1, and SPV-2 Low influent vapor concentrations and poor vacuum response in observation wells were observed during the test An air sparge test in SPV-1 increased the dissolved oxygen concentration from 0 5 to 2 4 mg/L in SPV-1 SITE LOCATION AND FACILITY DESCRIPTION The site is an active service station and convenience store located in a mixed residential and commercial area at the southwest corner of the intersection of March Lane and Da Vinci Drive in Stockton, California (Figure 1) The site is located to the south of an operating Carl's Jr restaurant The service station consists of a 7-Eleven convenience store with two 10,000-gallon USTs and two dispensers The dispenser islands and UST areas are paved with concrete and the remainder of the . site is surfaced with asphalt A portion of the dispenser islands and UST concrete pads were removed during the fuel line upgrade activities FIELD ACTIVITIES Dispenser Sample Collection and Analyses On April 4, 2003, SECOR's field scientist collected a total of two soil samples from native sod, one from beneath the southern fuel dispenser and one along the product line trenching connecting the dispensers A soil sample was not collected from beneath the northern dispenser due to the depth of pea gravel at the location 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 then pounded a sample tube into the sod in the center of the auger The sample tube was filled completely with sod to minimize headspace and sealed using Teflono 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 A and the soil sample locations are shown on Figure 1 The soil samples were analyzed for total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, and total xylenes (BTEX), MtBE, di-isopropyl ether (DIPS), tert-amyl-methyl ether (TAME), ethyl-t-butyl ether (ETRE), and tert-butyl alcohol (TBA) using EPA Method 82606 Soil samples were also analyzed for total lead using EPA Method 6010B i File 7-Eleven/Store 206MReports/20632 Fuel Line Upgrade Report doc SECOR International Incorporated