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the well (one well casing volume). Measurements are made to the nearest 0.01 foot and refer- <br /> enced to the permanent surveyed reference point on the well casing. <br /> C.6.3 Well Purging <br /> To ensure that the sample collected is as representative as possible of groundwater in the aquifer, <br /> standing water in the well and the surrounding sand pack is purged. Between four and six casing <br /> volumes of well water is purged to ensure that all stagnant water has bzen removed. The well is <br /> purged with submersible,airlift,or surface pumps or bailers,decontaminated as described above <br /> in Section C.6.1. <br /> Should the well pump dry after the casing is initially dewatered,purging is discontinued and thz <br /> well allowed to recover. Purging is continued to obtain the desired purge volume. <br /> Field parameters of pH,temperature, and electrical conductance are measured as the well is <br /> purged. Measurements are taken and recorded approximately every five gallons. If any of the <br /> three field parameters has not stabilized by the time the 4-6 casing volumes have been purgt d, <br /> additional well water is pumped until the parameters have stabilized (but no more than 10 casing <br /> volumes). "Stabilized" is defined as a reading less than 10 percent of a previous reading. <br /> All purge water is contained in 55-gallon drums labeled with well number,date,contents, and <br /> facility 4dentification. After the well has been purged of the required volume of water,the purg- <br /> ing equipment is removed. A Teflon sampling bailer is used to collect four separate samples for <br /> presample field parameter measurements, to confirm field parameter stability and, therefore, <br /> representative aquifer samples. <br /> C.6.4 Well Sampl_i«e <br /> All samples are collected with a Teflon bailer cleaned as discussed in Section C.6.1. The bailer <br /> is operated by hand on a new, 1/4-inch polypropylene rope or on Teflon-coated stainless steel <br /> wire. The sampling personnel wear clean Nitrile gloves during sampling operations and while <br /> handling sample bottles. <br /> The collected groundwater samples are emptied from the bailer with a bottom-emptying device <br /> directly into the sample bottles. The samples are collected in either 40-m1 glas- VOA vials or 1- <br /> liter amber bottles with Teflon-lined rPptum caps. The sample bottles contain appropriate pre- <br /> servatives,typically hydrochloric acid. The samples are contained in the containers free of head- <br /> space (i.e.,no air bubbles in the containers). <br /> The containers containing the samples are labeled with the well number,date, location, sampler's <br /> initials,and preservative in indelible ink, and the sample labels are covered with clear waterproof <br /> tape. <br /> c67/97780/apc C-4 <br />