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September 8, 1992 Working To Restore Nature <br /> ARCO Station No. 2076, Lodi, California <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 technician <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 technician, updated throughout handling of the samples, and sent along with the <br /> samples to the laboratory Copies of Chain of Custody Records will be included in our final <br /> report <br /> Gradient Evaluation <br /> The local groundwater 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 /> measurements will be made to the nearest 0 01 foot in each well with an electric water-level <br /> indicator The well will be vented to the atmosphere for a minimum of 1 hour before <br /> obtaining depth-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 ground-water surface in each well and the slope of the ground-water surface across <br /> the site <br /> Va or-Extraction Well Installation <br /> A schematic diagram of a vapor-extraction well is attached (PIate 3) The wells will be <br /> constructed of thread-jointed, 4-inch-diameter schedule PVC casing No chemical cements, <br /> glues, or solvents will be used in well construction The screened portion of the wells will <br /> consist of factory-perforated casing with 0 10-inch-wide slots The interval between 15 and <br /> 30 feet below grade will be screened using slotted casings Special Blend/Pea gravel will <br /> be placed in the annular space opposite the screen to approximately 1 foot above the top <br /> of the slotted casing A 2-foot bentonite plug will be placed above the sand pack, and a <br /> cement-bentonite slurry will be used to fill the remaining annulus to the surface <br /> A traffic-rated cast-aluminum utility box with a PVC apron will be placed over each <br /> wellhead and set in concrete flush with the surrounding concrete pad <br /> 30MB-5w <br />