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' perched water Thus, the borehole was filled with bentonite at the silt <br /> layer and well screening was set in the gravels above the silt layer. <br /> Confined ground water conditions were also encountered in MW-3A <br /> and MW-4A. At MW-3A, a 10-foot screened interval is located <br /> between 15 and 25 feet bgs This interval was chosen because no <br /> 1 ground water was initially encountered in this boring until a depth of <br /> approximately 19 feet bgs After the ground water was encountered, <br /> the water level rose within the boring to a final depth of <br /> approximately 3 5 feet bgs. To protect the upper sods from possible <br /> petroleum constituents in feet bgs he uppermosound water,t 15�feet of th scasing was placed <br /> to depth of 15 boring <br /> g <br />' contained mostly clays and silts, with minor amounts of sand. <br /> In MW-4A, ground water was encountered at an approximate depth <br /> of 19 feet bgs. After the ground water was' initiallyyapproximately o 5tered, the <br /> level subsequently rose to a depth of <br /> Therefore, the screened interval in this well was placed between 15 <br /> and 25 feet bgs <br /> Nion• installation <br /> Each monitoring well <br /> was developed immediately after ins tall to a equilibrate brace fog a r period <br />' minutes. The wells were subsequently q <br /> of one week beforesubsequent <br /> Well purging <br /> eve opment records are ling ti eluded vities �n <br /> place on April 3, <br /> Appendix M. <br /> 4n May 12, 1992, the wells were surveyed for elevation and location <br />' (Appendix M). The elevations of the tops of the well casings were <br /> measured with respect to the same benchmark that had been used <br /> during previous investigations at Site #1. An arbitrary base elevation <br />' of 100 feet was utilized, as in previous investigations. <br /> Purging purging was accomplished <br /> by removing a minimum of three well volumes of water. Water levels <br /> were measured before and after purging. The purged water was <br /> monitored for conductivity, temperature, pH, and turbidity <br /> All purge water and ansate was stored in sealed 55-gallon drums <br /> pending the results of laboratory <br /> nd boring number analyses Each dThe drums were <br /> m was clearly <br /> labelled to indicate its contents <br /> stored on site adjacent to the stockpiled soil. <br /> All wells except for MW-2A were sampled using a precleaned <br /> TeflonO bailer. The samples were not filtered in the field A ground <br /> water sample from MW-2A was not collected because floating <br /> product was observed in the bailed water from this well The floating <br /> ' product thickness measured less than 0 01 feet. <br /> 5-7 <br /> t , <br />