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� s <br /> November 18, 1991 — <br /> ARCO Station No. MO, Stockton, California <br /> Department of Transportation until suitable disposal options can be selected based on <br /> laboratory analysis. Disposal of drums and purge water is the responsibility of ARCO. <br /> The wells will be allowed to recover to at least 80 percent of static conditions, and a sample <br /> of the formation water will be collected with a Teflon bailer cleaned with a laboratory-grade <br /> detergent and deionized water. The water will be transferred slowly from the bailer to ' <br /> laboratory cleaned, 1-liter amber bottles and 40-milliliter glass vials for analyses by the <br /> laboratory. The glass vials will contain hydrochloric acid as a preservative. Our geologist ? <br /> will check to see if headspace is present. If headspace is present, we will collect more <br /> samples until a headspace is absent. Chain of Custody Records will be initiated in the field <br /> by the geologist, updated throughout handling of the samples, and sent along with the t <br /> samples to the laboratory. Copies of Chain of Custody Records will be included in our final <br /> report. <br /> radient Evaluation <br /> The local ground-water gradient will be evaluated to provide an indication of the direction <br /> of groundwater flow at the site. The elevation of the top of each well casing will be <br /> measured relative to mean sea level by a licensed land surveyor. Water-depth <br /> J measurements will be made to the nearest 0.01 foot in each well with an electric water-level <br /> indicator. The well will be venter: to the atmosphere for a minimum of 1 hour before <br /> obtaining death-to-water measurements. Venting is conducted to allow the ground water <br /> to equilibrate to barometric pressure. This data will be combined to evaluate the elevation <br /> of the groundwater surface in each well and the slope of the ground-water surface across <br /> 1 the site. <br /> i <br /> j <br /> 7' 3-4w _ <br />