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B.6.3 Well Purging To ensure that the sample collected is as representative as possible of groundwater in the aquifer, standing water in the well and the Surrounding sand pack is purged Between 4 and 6 casing volumes of well water are purged to ensure that all stagnant water has been removed The well is purged with a submersible, airlift, or surface pump or with a bailer, decontaminated as described above in Section B 6 1 ' Should the well pump dry after the casing is initially dewatered, purging is discontinued and the well allowed to recover Purging is continued to obtain the desired purge volume ' Field parameters of pH, temperature, and electrical conductance are measured as the well is purged Measurements are taken and recorded approximately every 5 gallons If any of the three field parameters has not stabilized by the time the 4-6 casing volumes have been purged, additional well water is pumped until the parameters have stabilized (but no more than 10 casing volumes) "Stabilized" is defined as a change in the reading amounting to less than 10 percent of the previous reading All purge water is contained in 55-gallon drums labeled with well number, date, contents, and facility identification After the well has been purged of the required volume of water, the purging equipment is removed A Teflon sampling bailer is used to collect four separate samples for presample field parameter measurements, to confirm field parameter stability and, therefore, representative aquifer samples B 6.4 Well Sampling ' All samples are collected with a Teflon bailer cleaned as discussed in Section B 6 1 The bailer is operated by hand on a new, 114-inch polypropylene rope or on Teflon-coated stainless steel wire The sampling personnel wear clean Nitrile gloves during sampling operations and while handling sample bottles ' The collected groundwater samples are emptied from the bailer with a bottom-emptying device directly into the sample bottles The samples are collected in either 40-m1 glass VOA vials or ' 1-liter amber bottles with Teflon-lined septum caps The sample bottles contain appropriate preservatives, typically hydrochloric acid The samples are contained in the containers free of headspace (i e , with no air bubbles) tThe filled sample containers are labeled with well number, date, location, sampler's initials, and preservative in indelible ink, and the sample labels are covered with clear waterproof tape The sample vials are placed in an iced cooler for delivery to a DHS-certified laboratory for analysis Standard chain-of-custody procedures are followed 1 ' WP61 73942 ROi397 APB I B-4