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KL /E NFELDER <br /> 8,hl Geopk.WIM 50.6.m <br /> • <br /> The wells will be constructed in 8-inch diameter boreholes. <br /> Well screen sections are perforated with 0.010- or .020-inch factory-cut slots. <br /> This parameter is assessed (and modified if required) after the boring logs <br /> and, if warranted, a sieve test has been performed and the results received. <br /> The wells are generally screened from 5 feet above to 20 feet below first <br /> groundwater. The screen length is reduced if an aquitard with a minimum <br /> thickness of 5 feet is encountered. If an aquitard is encountered the well is <br /> usually terminated 1 to 2 feet into the aquitard. Effort is made not to screen <br /> across two aquifers. If confined aquifer conditions or high vadose zone <br /> contamination is encountered, the well screen is usually not set above the <br /> depth of first encountered ground water. Wells are usually not set in areas of <br /> suspected significant soil contamination. <br /> • The PVC pipe and end caps are steam-cleaned prior to installation. <br /> The annular space between the screen and the wall of the boring is backfilled <br /> with the appropriate clean Lone Star Industries 0/30 or 2/12 Monterey sand to <br /> approximately 2 feet above the top of the perforated sections. Based on soil <br /> logs or a sieve test, modifications may be made regarding the size of sand to <br /> be used. Installation of the 0/30 sand may require that the sand be tremmied, <br /> using clean water. In this event, a sample of the tremie water is collected, <br /> unless the source is 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 /> • <br /> 117226.E02/ST012RO696 Page A-4 September 14, 2012 <br /> Copyright 2012 Kleinfelder <br />