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• September 15, 1993 Working To Restore Nature A. Tetchert & Son, Tracy, California Monitoring-Well Construction Monitoring wells were constructed in the borings with thread-pointed,2-inch-inner-diameter, • Schedule 40 PVC casing No chemical cements, glues, or solvents were used in well construction. The screened portion of each well consisted of factory-perforated casing with 0 020-inch-wide slots The well screen extends from the total depth of the well to approximately 5 or 10 feet above the groundwater surface This screened interval allows sampling at the air-water interface during seasonal fluctuations of the groundwater level The annular space in the well was packed with number 3 sand to approximately 1 to 2 feet above the slotted interval A 2- to 3-foot thick bentonite plug was added above the sand pack to prevent the cement from entering the well pack The remaining annulus was backfilled to grade with a bentonite cement slurry • Monitoring wells were 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 • We waited a minimum of 24 hours after well installation before developing the groundwater monitoring wells to allow the grout to seal Before developing the monitoring wells, a water sample was collected for subjective analysis from near the water surface in the well with a Teflon bailer cleaned with a laboratory-grade detergent and deionized water Floating • product was not encountered The wells were developed with a surge block and pump Well development continued until the discharge water was clear of silt and sand Clay-size sediments derived from the screened portion of the formation cannot be entirely eliminated by well development. After the wells stabilized for a minimum of 24 hours, the wells were purged of stagnant water and a sample was collected for laboratory analysis The well was 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 was stored in labeled, 55-gallon, steel drums approved for this use by the Department of Transportation until suitable disposal options were selected based on laboratory analysis Groundwater Sampling i The static water level in each well was measured to the nearest 0 01 foot with a Sohnst • electric water-level sounder cleaned with a laboratory-grade detergent and deionized water 0803gtak 123009.1 0