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Broadbent&Associates,Inc. Vacaville,California Site Assessment Work Plan Former ARCO Station No.443 November 8,2013 Page No.v compromised. A sample will still be collected but will be marked as "flagged"with a note explaining that the helium test had failed. 3.5 Soil Gas Sampling and Analysis Soil gas samples will be collected in Summa canisters after a successful completion of shut in and leak tests and after three casing volumes of soil gas are purged. The soil gas will be removed at a rate between 100 and 200 ml/min. The Summa canister label will contain the information such as sample identification,starting and ending vacuum readings,sample date,and time. The details of field activities,site conditions, and data collected will be recorded on field forms. The soil gas samples will be sent for analysis to a State Certified Laboratory. Analysis will be performed by appropriate United States Environmental Protection Agency(USEPA)or equivalent methods and will consist of GRO, benzene,toluene, ethyl-benzene,xylenes, 1, 2 DCA, carbon dioxide, methane,oxygen, and nitrogen. 3.6 Soil Sampling and Analysis A Broadbent field geologist will observe a California C-57 licensed driller advance two soil borings at the approximate locations identified on Drawing 2. The borings will be advanced using a hand auger to an approximate depth of up to 10 feet bgs. Soil samples will be collected at a depth between 0 and 5 feet bgs and another at 5 and 10 feet bgs from each location. Soil samples will also be collected from the soil gas wells. The samples will be collected into clean brass tubes by driving split-spoon sampler into undisturbed soils. Once collected,the ends of each sample tube will be covered with Teflon film, capped with plastic end caps, labeled, placed into a plastic bag,sealed and then placed into an ice chest cooled with synthetic ice for delivery to a State-certified analytical laboratory. The selected soil samples will be chemically analyzed for the presence and concentration of GRO by EPA Method 80156 and for benzene,toluene,ethylbenzene,and total xylenes, by EPA Method 8260.A State-certified analytical laboratory will conduct the chemical analyses. 3.7 Field Equipment Decontamination Procedures Field equipment that comes into contact with soil or groundwater will be decontaminated before each use by steam cleaning or washing in a laboratory-grade detergent solution,followed by tap water rinse. Potable water will be used for decontamination of drilling equipment. Rinse water used in the decontamination process will be contained in a labeled 55-gallon drum and temporarily stored at the site. 3.8 Well Surveying The soil boring and soil gas well locations will be surveyed by a California Licensed Professional Land Surveyor for horizontal controls. The survey point will be referenced to a known benchmark using the North American Vertical Datum of 1988(NAVD88)and the North American Datum of 1983 (NAD83). Survey information will be uploaded to State Water Resources Control Board Geotracker database.