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„ r • • packed with number 3 sand to approximately 1 to 2 feet above the slotted interval. A surged and refilled bentonite plug will be added above the sand pack to prevent cement from entering the well pack. The remaining annulus will be backfilled to grade with a slurry of cement and bentonite powder. The monitoring wells will be protected with a traffic-rated, cast-aluminum utility box equipped with a PVC skirt. The box has a watertight seal to protect against surface-water infiltration and must be opened with a special wrench. The design of this box discourages vandalism and reduces the possibility of accidental disturbance of the well. Well Development and Samoling ERI will wait a minimum of 24 hours before development of the monitoring wells to allow the grout to seal. Initially, a water sample will be collected for subjective analysis before development of the monitoring wells. This sample will be collected from near the water surface in the well with a Teflon® bailer cleaned with a laboratory-grade detergent and deionized water. The wells will be developed with a surge block and pump. Well development will continue until the discharge water is clear of silt and sand. Clay-size sediments derived from the screened portion of the formation cannot be eliminated by well development. After the well has been allowed to stabilize, the well will be checked for floating product using an interface probe. The thickness of any product detected in the well will be recorded. If floating product is encountered in the well, the well will not be purged, and the water will not be sampled for chemical analysis. Product will be bailed from the well and stored in appropriately labeled drums onsite. ERI will apprise Unocal of appropriate recycling options for product bailed from well. If no floating product is detected after development, the well will be purged of stagnant water and a sample will be collected for laboratory analysis. The well will be purged of approximately 3 to 5 well volumes of water with a submersible pump, or until pH, conductivity, and temperature of the purged water have stabilized. Water purged from the wells will be stored in labeled, 55-gallon, steel drums approved for this use by the Department of Transportation until suitable recycling options can be selected based on laboratory analysis. ERI will coordinate with Unocal for disposal of the purged water. The wells will be allowed to recover to at least 80 percent of static conditions, and a sample of the formation water will be collected with a new disposable Teflon®bailer. The water will be transferred slowly from the bailer to laboratory-cleaned, 1-liter amber bottles and 40-milliliter glass vials for analyses by the laboratory. The glass vials will contain hydrochloric acid as a preservative. The sampler will check to see if headspace is present. If headspace is present, the sampler will collect more samples until none is present. Chain of Custody Records will be initiated in the field by the geologist, updated throughout handling of the samples, and sent along with the samples to the laboratory. Copies of Chain of Custody Records will be included in our final report. Gradient Evaluation ERI will evaluate the direction of flow and gradient at the site. The elevation of the top of each well casing will be measured relative to mean sea level by a licensed land surveyor. Water-depth measurements will be made from the top of the casing in the well to the nearest 0.01 foot with an electronic water-level indicator. The well will be vented to atmosphere for a minimum of 0.5 to 1 hour before obtaining depth-to-water measurements. Venting is conducted to allow the groundwater to equilibrate with barometric pressure. These data will be combined to evaluate the relative elevation of the groundwater surface in each well and the slope of the groundwater surface across the site.