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• ` ,,. Fi' .. '' � n 1 , .;f' lid II <br /> I i <br /> logbook. The ground-water elevation at each monitoring well will'be,.cal- <br /> culated b subtracting the measured depth to water from the surveyed <br /> Y 9 P su; <br /> elevation of the top of the well casing. (Every attempt will be made to mea' !� <br /> sure .depth to water for all wells on the same da Total well de th will <br /> P Y <br /> P ' <br /> then be measured by lowering the sensor to the bottom of the well. Total ' <br /> well depth, used to calculate purge volumes and to determine whether the <br /> r well screen is partially obstructed by sift, will be recorded to the nearest <br /> 0.1 foot in.the field logbook. <br /> Well Purging <br />• Before the sampling event, a polyvinyl chloride bailer, low-flow :sub- <br /> mersible pump, or Teflon bailer will be used to purge standing water in 'the <br /> casing and gravel pack from the monitoring well. Monitoring wells will be <br /> purged according to the protocol presented in Figure B-1. In most moni- <br /> toring wells, the amount of water purged before sampling will be greater <br />« than or equal to five casing volumes. Some monitoring wells are expected <br /> to be evacuated to dryness after removing fewer than five casing volumes. <br /> These low-yield monitoring wells will be allowed to recharge for up to <br /> 24 hours. Samples will be obtained as soon as the monitoring wells have <br /> recharged to a level sufficient for sample collection. If insufficientwater <br /> has recharged after 24 hours, the monitoring well will be recorded as dry <br /> for the sampling event. <br /> Ground water purged from the monitoring wells will be containerized in <br /> 55-gallon drums for subsequent disposal. Drums will be stored on site at a <br /> ARCO-designated location. <br /> EMCON will arrange for the disposal of the purged ground water and the <br /> removal of drums through Balch Petroleum. During storage, drums will be <br /> properly labeled with a drum label. <br /> 0 Field measurements of pH, specific conductance and temperature will be <br /> recorded in a waterproof field logbook. Figure B-2 shows an example of.a <br /> Water Sample Field Data Sheet on which field data are recorded. Field <br /> data sheets will be reviewed for completeness by the sampling coordinator <br /> after the sampling event is completed. " <br /> The pH, specific conductance and temperature will be calibrated each day <br /> before field activities begin. The calibration will be checked once each day <br /> to verify meter performance. Field meter calibrations will be recorded on <br /> the Water Sample Field Data Sheet. <br /> PRO P91LO28.DOC Rev. 0 Febnnuy6, 1992 <br />