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Work Plan for Well Destruction Soil Stockpile Sampling and Excavation Backfill 2 Barbara Drake Site a.k.a.Ron's Corral 26485 North Thornton Road Thornton California Se tember 3 1997 out and removed, and an excavation will be dug to expose the casing and well seal to a depth of three feet below ground surface (bgs). The casing and well seal will be trimmed back,so that the casing extends approximately six inches above the bottom of the excavation. A neat cementfbentonite grout delivered via a tremie pipe will be used to backfill the well to the top of casing, and the well excavation area will be backfilled with grout to a depth of approximately two feet bgs. After the grout sets, clean on-site soil will be used to complete the backfill of the boring to the surface. Wells MW-2 and MW-3,which have historically contained varying concentrations of dissolved petroleum hydrocarbons,will be overdrilled with 10-inch-diameter hollow-stem augers using a truck-mounted drill rig to a depth of 20 feet bgs. The resultant borehole will then be backfilled with a neat cementlbentonite grout using a tremie pipe placed in the borehole. All well-related materials will be stockpiled on-site pending characterization and disposal by a waste-hauler. Soil Stockpile Sample Collection Prior to excavation backfill activities, Fluor Daniel GTI will obtain a total of sixteen separate composite soil samples from the stockpiled soil presently on-site. Prior to stockpile sampling,an access bore will be hand- augered into the stockpile at each sample point to an appropriate sample collection depth. Each sample will be collected by driving a 2-inch-diameter by 6-inch-long brass sleeve,fitted on the end of a slide hammer, into the stockpile. The hand auger and sampling equipment will be cleaned between each sampling interval. Soil will be screened for hydrocarbon vapors using a photo-ionization detector(PID). The sample tube from each sampling point will be sealed with Teflon sheets, capped,taped, labeled, and placed on ice in an insulated container.All samples collected will be combined into four composite samples and analyzed by a California-certified analytical laboratory for benzene,toluene, ethylbenzene and total xylenes (BTEX), and methyl tert-butyl ether(MTBE), and total petroleum hydrocarbons as gasoline (TPH-g) by Environmental Protection Agency(EPA) Methods 8020/8015 modified. In addition, samples will be analyzed for total petroleum hydrocarbons as diesel fuel (TPH-d)with silica-gel cleanup using EPA Method 8015 modified, and total lead using EPA Method 6010. Excavation Backfill Procedures Fluor Daniel GTI will supervise the backfilling of the former UST excavation. Because the bottom of the excavation is located within a local perched water zone, imported pea gravel will be used to backfill the excavation to a depth approximately that of historic high perched groundwater elevations. If the soil stockpile analytical results indicate the stockpile soil contains petroleum hydrocarbons or lead below minimum detection limits,soil from that stockpile will be used to complete the backfill of the excavation 20700512.wo FLUOR DANIEL GTI