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Work Plan for Additional Subsurface Investigation <br /> 7-Eleven Store#19976 1399 N Main St Manteca CA 2 <br /> Au ust 1,2000 <br /> Soil Gas Survey Procedure <br /> Ten soil-gas probes will be Installed using a truck-mounted hydraulic probe driver During sampling, a <br /> hollow 1-Inch-diameter Geoprobe rod with an expandable tip will be pushed and/or hammered to the <br /> sample depth The probe will be pulled up approximately 6 Inches allowing the tip to drop out, thus <br /> exposing a section of the subsurface materials Polyethylene post-run tubing (PRT)and a threaded <br /> adapter are inserted down the center of the Geoprobe rod, and threaded into a bottom adapter of the <br /> probe (sealing the exposed section of subsurface) One volume of soil-gas is purged from the PRT and <br /> the open interval prior to sampling Soil-gas samples are collected by connecting TeflonTm tubing to the <br /> PRT at each sample location The Teflon tube is connected to a control valve and a clean, one-liter <br /> Tedlar bag placed in a sealed vacuum box A vacuum is applied to the sealed box, thus filling the Tedlar <br /> bag with soil-gas Upon filling the Tedlar bag, the control valve is locked and the bag removed from the <br /> vacuum box <br /> Following sample collection, the soil-gas samples will be labeled and placed in a insulated container A <br /> total of ten samples will be collected and analyzed by a State-certified analytical laboratory for benzene, <br /> toluene, ethylbenzene and xylene( BTEX), methyl-tent-butyl-ether(MTBE)and total petroleum <br /> hydrocarbons-as-gasoline (TPH-G), by Environmental Protection Agency(EPA) methods 8020/8015 <br /> modified, and the oxygenates tert-butanol (TBA), MTBE, dnsopropyl ether(DIPS), ethyl-tert-butyl ether <br /> (ETRE), and tert-amylmethyl ether(TAME) by EPA method 8260, in addition to methanol, ethanol, and 1-2 <br /> dichloroethane (DCA), also by EPA Method 8260 <br /> Following sample collection, the drive rods will be removed, and the resultant borehole grouted with neat <br /> cement <br /> Groundwater Monitoring Well Installation <br /> An offsite, downgradient groundwater monitoring well will be drifted using a drilling rig equipped with an 8- <br /> inch diameter hollow-stem augers All drilling equipment will be steam cleaned prior to drilling each <br /> boring, and sampling equipment will be washed in a non-phosphate solution and rinsed with water <br /> between sampling intervals All soil and rinse water generated during the drilling will be placed in labeled <br /> Department of Transportation (DOT)-approved 55-gallon drums and left on the site pending transportation <br /> and disposal <br /> Soil samples will be collected during drilling at 5-foot intervals to total depth using a split-spoon sampler <br /> lined with 2-inch-diameter by 6-inch-long brass sample tubes The sample tubes will be sealed with <br /> Teflon pads, plastic caps and tape, labeled, placed on ice in an insulated container, and submitted for <br /> analyses under chain-of-custody manifest to a state-certified laboratory for analysis Soil samples will be <br /> field screened for hydrocarbon vapors using a flame-ionization detector(FiD) Soil will be logged using <br /> the Unified Sod Classification System by an IT Corporation field geologist working under the supervision of <br /> a California registered geologist <br />