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h <br /> �FSMA <br /> March 18, 1993 Working To Restore Nature <br /> ARCO Station No 5100, Tracy, California <br /> is then labeled and placed in iced storage Chain of Custody Records are initiated by the <br /> geologist and accompany the samples to the analytical laboratory <br /> i Va or-Extraction Well Construction <br /> The wells are constructed using clean 4-inch-inner-diameter, thread pointed, Schedule 40 <br /> polyvinyl chlonde (PVC) casing. No chemicals, glues, or solvents are used in construction of <br /> the wells. The screened portion of the vapor-extraction well consists of a S- and 10-foot <br /> sections of factory-perforated casing with slots Unperforated casing is set from the top of the <br /> screen to several inches below surface grade <br /> The annular space of each well is packed with pea gravel from the bottom of the screen <br /> portion 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 The remaining annulus is backfilled to the ground surface with a mixture of water, <br /> cement, and bentomte The construction details of the individual wells are shown on the Logs <br /> of Borings. <br /> The wellheads are secured in cast-aluminum utility boxes with PVC aprons The boxes have <br /> v 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 the <br /> well. Each wellhead is also fitted with a locking well cage to further protect against <br /> unauthorized disturbance of the well <br /> f <br /> Sample Labeling and Handling <br /> Sample containers are labeled in the field with the ,fob number, sample location and depth, <br /> and date and promptly placed in iced storage for transport to the laboratory. A Chain of <br /> Custody Record is initiated by the geologist and updated throughout handling of the samples <br /> and accompanies the samples to a laboratory certified by the State of California for the <br /> analyses requested Samples are transported to the laboratory promptly to help ensure that <br /> recommended sample holding times will not be exceeded Samples in our custody will be <br /> properly disposed of after their useful life has expired <br /> 1 <br /> 1 <br /> 1231ccar <br /> 30041-4 <br />