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r E� 1 o The well casing will be 2-inch inside diameter, flush threaded joint, schedule 40 PVC pipe. o The wells will be constructed in 8-inch diameter boreholes. �:• o Well screen sections are perforated with 0.010- or .02411ch factory-cut slots. This parameter is assessed (and modified if required) after the boring logs and,if warranted, a sieve test has been performed and the results received. o The wells are generally screened from.5 feet above to 20 feet below first ground water. The screen length is reduced if an aquitard with a minimum thickness of 5 feet is encountered. If an 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 ground water. Wells are usually not set in areas of suspected significant soil contamination. o The PVC pipe and end caps are steam cleaned prior to installation. o The annular space between the screen and the wall cf 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 u 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 known to be clean. o A 3-to 5-foot bentonite plug is placed above the sand pack to provide a seal against surface water infiltration. o The remaining annular space is filled to the surface with tremmied cement/bentonite grout to the surface. o The wells are secured in a locking stovepipe. The well heads may be enclosed in a cement utility box set flush to the ground surface located in a traffic area. F6-FIELDPRO