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KLEINFELDER <br /> The wells are generally screened from 5 feet above to 20 feet below first ground <br /> water The screen length is reduced if an aquitard with a minimum thickness of 5 <br /> feet is encountered if an aquitard is encountered the well is usually terminated 1 <br /> to 2 feet Into the aquitard Effort is made not to screen across two aquifers If <br /> confined aquifer conditions or high vadose zone contamination is encountered, the <br /> well screen is usually not set above the depth of first encountered ground water <br /> Wells are usually not set in areas of suspected significant soil contamination <br /> I <br /> • The PVC pipe and end caps are steam cleaned prior to installation <br /> i <br /> • The annular space between the screen and the wall of the boring is backfilled with <br /> the appropriate clean Lone Star Industries 0130 or 2112 Monterey sand to <br /> approximately 2 feet above the top of the perforated sections Based on soil logs <br /> or a sieve test, modifications may be made regarding the size of sand to be used <br /> Installation of the 0130 sand may require that the sand be tremmied, using clean <br /> water In this event, a sample of the tremie water is collected, unless the source is <br /> known to be clean <br /> . • A 3- to 5-foot bentonite plug is placed above the sand pack to provide a seal <br /> against surface water infiltration <br /> • The remaining annular space is filled to the surface with tremmied <br /> cement/bentonite grout to the surface <br /> • The wells are secured in a locking stovepipe The well heads may be enclosed in <br /> a cement utility box set flush to the ground surface located in a traffic area <br /> B-3 2 Monitoring Well Development and Sampling <br /> The wells are developed to reduce the effects of drilling on the formation and to increase the <br /> effective hydraulic radius of the well <br /> Monitoring wells are generally developed 24 to 48 hours after installation to allow the grout to <br /> set Each well is first sampled with a clear acrylic bailer to visually inspect for hydrocarbon <br /> layer or sheen If no product layer or sheen is observed on the water, the well is developed by <br /> surging, pumping, or bailing Surging along the screened interval of the well is performed to <br /> • draw the sediment from the formation into the filter pack and the well and to set the sand pack <br /> 40-YP9179/401 OPO 19 10 <br /> Copyright 2000 Kleinfelder Inc <br />