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laboratory Copies of these records are in our report Cuttings generated during drilling are placed on plastic sheeting and covered and left at the site ERI coordinates with Tosco for the soil to either be treated on site or removed to an appropriate recycling or disposal facility MonituKing Well Monitoring wells are constructed in borings using thread-jointed, 2-inch inner diameter, Schedule 40 polyvinyl chloride (PVC) casing No chemical cements, glues, or solvents are used in well construction The screened portion of each well consists of factory-perforated casing with 0 020-inch wide slots If unconfined aquifer conditions exist, the well screen is installed from the total depth of each well to approximately 10 feet above the uppermost water-bearing unit If confined conditions exist, the uppermost water-bearing unit is screened exclusively Unperforated casing is installed from the top of each screen to the ground surface The annular space in the well is packed with #3 sand to approximately 1 to 2 feet above the slotted interval A bentonite plug is added above the sand pack to prevent cement from entering the well pack The remaining annulus is backfilled to grade with a slurry of portland cement ' The monitoring wells are 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 Sampling ERI waits a minimum of 24 hours before development of the monitoring wells to allow the grout to seal Initially, a water sample is collected for subjective analysis before development of the monitoring wells This sample is collected from near the water surface in the well with a Teflon®bailer cleaned with a laboratory-grade detergent and deionized water The wells are developed with a surge block and pump Well development continues 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 is checked for floating product using an interface probe The thickness of any product detected in the well is recorded If floating product is encountered in the well, the well is not purged, and the water is not sampled for chemical analysis Product is bailed from the well and stored in appropriately labeled drums on site ERI apprises Tosco of appropriate recycling and disposal options for product bailed from the well iIf no floating product is detected after development, the well is purged of stagnant water and a sample is collected for laboratory analysis The well is purged of approximately three to five well volumes of I water with a submersible pump, or until pH, conductivity, and temperature of the purged water have stabilized Water purged from the wells is stored in labeled, 55-gallon, steel drums approved for this use by the Department of Transportation until suitable disposal options can be selected based on ' laboratory analysis ERI coordinates with Tosco for recycling or disposal of the purged water The wells are allowed to recover to at least 80 percent of static conditions, and a sample of the formation water is collected with a Teflon® bailer cleaned with a laboratory-grade detergent and deionized water The water is 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 contain hydrochloric