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August 18, 1993 <br />. Unocal Service Station No 6981, Stockton, California Working To Restore Nature <br /> Soil borings will be drilled with a CME-55 (or similar) drill rig equipped with 10-inch <br /> diameter, hollow-stem augers Auger flights and sampling equipment will be steam-cleaned <br /> before use in each borehole to minimize the possibility of downhole or crosshole <br /> contamination Drilling will be performed under the observation of a field geologist, and <br /> the earth materials in the borings will be identified using visual and manual methods, and <br /> classified using the Unified Soil Classification System as drilling progresses <br /> During drilling of the soil borings, soil samples will be collected at 5-foot intervals, obvious <br /> changes in soil stratigraphy, and at the base of each boring Samples will be collected with <br /> a California-modified, split-spoon sampler equipped with clean brass sleeves Samples will <br /> be collected by advancing the auger to a point ,lust above the sampling depth and driving <br /> the sampler into the undisturbed soil The sampler will be driven 18 inches with a standard <br /> 140-pound hammer repeatedly dropped 30 inches The number of blows required to drive <br /> the sampler each successive 6-inch interval will be counted and recorded to give an <br /> indication of soil consistency <br /> Soil samples will be evaluated with a photoionization detector (PID), which measures <br /> hydrocarbon concentrations in the ambient air or headspace above the soil sample Field <br /> instruments such as the PID can be useful for providing a preliminary assessment of the <br /> relative levels of hydrocarbon vapor The PID does not detect concentrations of <br /> hydrocarbons with the same precision as laboratory analyses Soil samples selected for <br /> possible chemical analysis will be sealed quickly with teflon foil, plastic caps, and tape The <br /> samples will be labeled and placed in iced storage for transport to the laboratory Chain <br /> of Custody Records will be initiated by the geologist in the field and will accompany the <br /> samples to the laboratory <br /> Cuttings generated during drilling will be stockpiled at the site on plastic sheeting and will <br /> be covered with plastic Four soil samples will be collected from the drill cuttings These <br /> 38032-14w 7 <br />