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June 30, 1992 ����JA <br /> Unocal Station No 6981, Stockton, California <br /> SamRling Drill Cuttings <br /> Soil samples are collected from the stockpiled soil by driving a hand-operated percussion <br /> sampler fitted with a clean brass sleeve into the stockpiled soil The sleeve is removed from <br /> the sampler and promptly sealed with aluminum foil, plastic caps, and duct tape. The <br /> sample is then labeled and placed in iced storage Chain of Custody Records are initiated <br /> by the geologist and accompany the samples to the analytical laboratory <br /> Well Construction <br /> The wells are constructed using clean 2-, 4-, or 6-inch-inner-diameter, thread jointed, <br /> Schedule 40 polyvinyl chloride (PVC) casing No chemicals, glues, or solvents are used in <br /> construction of the wells The screened portion of the monitoring well consists of factory- <br /> perforated casing with slots and extends from the total depth of the bonng to about S feet <br /> above the depth where water is first encountered. The screened portion of the vapor- <br /> extraction well consists of a 10-foot section of factory-perforated casing with slots and <br /> extends from the approximately 1 foot above the depth where water was first encountered <br /> Unperforated casing is set from the top of the screen to several inches below surface grade <br /> The annular space of each well is packed with sorted sand from the total depth of the <br /> boring to approximately 1 foot above the top of the screen A plug of bentonite pellets <br /> (approximately 2 feet thick) was placed above the sand to prevent cement from entering the <br /> sand pack This seal reduces the possibility that hydrocarbons migrating downward through <br /> the overlying sand will infiltrate the aquifer The remaining annulus is backfilled to the <br /> ground surface with a mixture of water, cement, and bentonite. The construction details of <br /> the individual wells are shown on the Logs of Borings <br /> The wellheads are secured in cast-aluminum utility boxes with PVC aprons. The boxes have <br /> watertight seals and are set in concrete approximately flush with the surrounding ground <br /> surface to reduce surface-water infiltration A special wrench is required to open the box <br /> This design discourages vandalism and reduces the possibility of accidental disturbance to <br /> the well. Each wellhead is also fitted with a locking well cage to further protect against <br /> unauthorized disturbance of the well. <br /> 0 <br /> 3832-7 <br /> 38032-7 <br />