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' k'q KLEINFELDER <br /> 1 <br /> i A-a GROUNDWATER WELL INSTALLATION <br />' A-3.1 Monitoring Well Construction <br /> Construction details for shallow groundwater monitoring wells are as follows <br />' • The monitoring wells will have casings consisting of 2-inch inside diameter, flush- <br /> threaded joint, Schedule 40 PVC pipe These wells will be constructed in 8-inch <br /> diameter borings <br />' • Well screen sections will be perforated with 0 010- or 0 020-inch factory-cut slots <br /> The perforation sieve openings are assessed (and modified if required) after the <br /> tborings are logged, and if warranted, a sieve test has been performed and the results <br /> received <br /> • The wells are generally screened from 5 feet above to 15 feet below first <br /> groundwater If an apparent aqultard is encountered, the well is usually terminated <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 in usually not set above the depth of first encountered groundwater <br /> Wells are usually not set in areas of suspected significant soil contamination <br /> • The PVC pipe and end caps will be steam cleaned prior to installation <br /> • The annular space between the screen and the wall of the boring is backfilled with <br />' the appropriate clean Lone Star Industries 0/30 or 2112 Monterey sand to <br /> approximately 2 feet above the top of the perforated sections Based on soil logs or <br /> a sieve test, modifications may be made regarding the size of sand to be used <br /> tInstallation of the 0/30 sand may require that the sand be tremmied, using clean <br /> water In this event, a sample of the tremae water is collected, unless the source is <br />' thought to be clean <br /> • A 3- to 5-foot bentonite plug is placed above the sand pack to provide an annular <br />' seal against surface water infiltration and to reduce the potential for cement grout to <br /> infiltrate into the water <br />' • The remaining annular space is filled to the surface with tremmied <br /> cement/bentonite grout(sin-face seal) to the surface <br /> e The wells will be secured in a below-ground locking stovepipe and the well heads <br /> enclosed in a water-tight cement utility box set flush to the ground surface <br /> DH and 7E194 Paige in of v <br />' Copyright 1994, Kletnfelder, Inc <br />