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r M KLEINFELDER A-3 GROUNDWATER WELL INSTALLATION A-3.1 Monitoring Well Construction Construction details for shallow groundwater monitoring wells are as follows: • The monitoring wells W.ili have casings consisting of 2-inch inside diameter, flush- threaded joint, Schedule 40 PVC pipe. These wells will be constructed in 8-inch diameter borings. • Well screen sections will be perforated with 0.010-inch or 0.020-inch factory-cut slots. The perforation sieve openings are assessed (and modified if required) after the borings are logy"ed and if warranted, a sieve test has been performed and the results received. • The wells are generally screened fro11i 5 feet above to 15 feet below,first groundwater. 11' an apparent aquitard is encountered, the well is usually terminated to 2 feet into the aquitard. I-Hfo.rt is :made riot to screen across two aquifers. If confined aquifer conditions or high vaclose 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 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 salad to be used. Installation of the 0/30 salad niay require that the sand be tremmied, using clean water. In this event, a sample of the t.remie water i5 collected, unless the source is thought to be clean. • A 3-foot to 5-foot bentonite plug is placed above the sand pact: to provide an annular seal against surface water Inf Itratiou and to reduce the potential for cement grout to infiltrate into the water. • The remaining annular space is billed to the surface with tremmied cement/bentonite grout (surface seal) to the surface. • 'l he 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. 20-Y P8-12412(}I X11 141/20 1 fSC:270 Page A-3 © 1998, Kleinlclder. Inc. 3u11c 16, 1998