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Well Purging <br />' Before the sampling event, a bladder pump, pneumatic displacement <br /> pump, or Teflon bailer will be used to purge standing water in the casing <br />' and gravel pack from the monitoring well. Monitoring wells will be purged <br /> according to the protocol presented in Figure C-1 . In most monitoring <br /> wells, the amount of water purged before sampling will be greater than or <br /> equal to four casing volumes. Some monitoring wells are expected to be <br /> evacuated to dryness after removing fewer than four casing volumes. <br /> These low-yield monitoring wells will be allowed to recharge for up to <br /> 24 hours. Samples will be taken as soon as the monitoring wells have <br /> recharged to a level sufficient for sample collection. If insufficient water <br /> has recharged after 24 hours, the monitoring well will be recorded as dry <br /> for the sampling event. <br /> Field measurements will be recorded in a waterproof field logbook. Fig- <br /> ure C-2 shows an example of the Water Sample Field Data Sheet on <br /> which field data are recorded. Field data sheets will be reviewed for com- <br /> pleteness by the sampling coordinator after the sampling event is com- <br /> pleted. <br /> The pH, specific conductance, and temperature meter will be calibrated <br /> each day before field activities begin. The calibration will be checked once <br /> each day to verify meter performance. Field meter calibrations will be <br /> recorded on a Field Nieter Log Form (see Figure C-3). <br />' Well Sampling <br /> A Teflon bailer or bladder pump will be the only equipment acceptable for <br /> well sampling. When samples for volatile organic analysis are being <br /> col-lected, the pump flow will be regulated at approximately 100 milliliters per <br /> minute to minimize pump effluent turbulence and aeration. Glass bottles of <br />' at least 40-milliliters volume and fitted with Teflon-lined septa will be used <br /> in sampling for volatile organics. These bottles will be filled completely to <br /> prevent air from remaining in the bottle. A positive meniscus forms when <br />' the bottle is completely full. A convex Teflon septum will be placed over <br /> the positive meniscus to eliminate air. After the bottle is capped, it is <br /> inverted and tapped to verify that it contains no air bubbles. The sample <br />' containers for other parameters will be filled, filtered as required, and <br /> capped. <br /> ' pj#V92V920201 a C - 4 Rev. 0 June 1, 1992 <br /> 1 <br />