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hn KLEINFELDER A-3.6 SOIL CUTTING DISPOSAL Drill cuttings will be placed in 55-gallon drums and left on site for disposal by the site owner. If requested, Kleinfelder can coordinate disposal of soil and water after analytical results are available. A-4 GROUNDWATER WELL INSTALLATION A-4.1 MONITORING WELL CONSTRUCTION Construction details for shallow groundwater monitoring wells are as follows: • The well casing will be 2-inch inside diameter, flush threaded joint, schedule 40 PVC pipe. • The wells will be constructed in 8-inch diameter borings. • Well screen sections will be perforated with 0.010- or .02-inch factory-cut slots, depending upon field observations. • The wells are generally screened from 5 feet above and 10 to 15 feet below first groundwater. The screen length is reduced if an aquitard with a minimum thickness of 5 feet is encountered. 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 is 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 are 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 0/30 or 2/12 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 tremie 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 a 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 cement/bentonite grout to the surface. • The wells are secured in an above- or below-ground locking stovepipe. The well heads may be enclosed in a water tight cement utility box set flush to the ground surface when located in a traffic area. 23-482276-B00/CR96S070 A-5 June 26 1996 Copyright 1996 Kleinfelder,Inc.