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,} J KLEINFELDER File No. 20-3769-01 March 16, 1994 • Well screen sections will be perforated with 0 010-or 0.020-inch factory-cut slots. The perforation sieve openings are assessed (and modified if required) after the borings are logged, and if warranted, a sieve test has been performed and the results received. • The wells are generally screened from 5 feet above to 15 feet below first groundwater. Due to shallow groundwater at the site, the screen length may be reduced to 10 feet below first encountered groundwater. If an apparent aquitard is encountered, the well is usually terminated 1 to 2 feet into the aquitard. Effort is made not to screen across two aquifers. If confined aquifer conditions or high vadose zone contamination is encountered, the well screen in usually not set above the depth of first encountered groundwater. Wells are usually not set in areas of suspected significant soil contamination. • The PVC pipe and end caps will be steam cleaned prior to installation. • The annular space between the screen and the wall of the boring is backfilled with the appropriate clean Lone Star Industries 0130 or 2112 Monterey sand to approximately 2 feet above the top of the perforated sections. Based on soil logs or a sieve test, modifications may be made regarding the size of sand to be used. Installation of the 0/30 sand may require that the sand be tremmied, using clean water. In this event, a sample of the tremae water is collected, unless the source is thought to be clean. • A 3- to 5-foot bentonite plug is placed above the sand pack to provide an annular seal against surface water infiltration and to reduce the potential for cement grout to infiltrate into the water. • The remaining annular space is filled to the surface with tremmied cementlbentonite grout (surface seal) to the surface. • The wells will be secured in a below-ground locking stovepipe and the well heads enclosed in a water-tight cement utility box set flush to the ground surface. A-3.2 Monitoring Well Development The wells are developed to reduce the effects of drilling on the formation and to increase the effective hydraulic radius of the well. Monitoring wells are generally developed 24 to 48 hours after installation to allow the grout to set. Each well is first sampled with a clear acrylic bailer to visually inspect for hydrocarbon layer or sheen. If no product layer of sheen is observed on the water, the well is developed by surging, pumping, or bailing. Surging along the screened interval of the well is performed to 40 draw the sediment from the formation into the falter pack and the well and to set the sand pack. The sediment-laden water is purged from the well at a rate of between 0 75 to 10 gallons per Copyzight 1994 Kleinfoldsr, Inc Pago 3 of 5