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Groundwater Sampling SOP Revision Na 0 Date January 01. 1995 Page 2 of S • Reagent Grade Methanol rinse (the equipment shall be thoroughly wetted with Methanol), • Analyte-free water rinse, • Air dry WATER LEVEL MEASUREMENTS : A complete round of water level measurements must be collected prior to any purging or sampling activities Water level measurements, using an electronic water level indicator, should be taken to the nearest 0 01 foot Where possible water level measurements shall be taken on the North Side of the monitoring well at the top of the casing, unless a measurement point has been previously established PURGING STATIC WATER • All information concerning the purging of static water including calculations must be recorded for each well The type of equipment used to purge the well must be described in the logbook If a pump is utilized information concerning the pump type and flow-rate must be included in the logbook • When a bailer is used for purging and/or sampling activities it must be lowered gently into the well such that the formation waters are disturbed as little as possible It is very important that the turbidity of the sample not be increased by improper purging and/or sampling techniques • A minimum of three well volumes of the standing water column will be purged from the well prior to the collection of samples Monitoring well purging will continue until groundwater temperature, pH, and specific conductance has stabilized for three measurements each following the removal of one well volume If five well are removed then, only one set of water quality measurements is required on final purge volume No more than five wells volumes shall be removed during purging activities over purging the well may result in the collection of non-representative groundwater samples If the well does not recover quickly enough to permit the removal of three well volumes, the well will be pumped or bailed dry and sampled immediately following sufficient recovery Generally, bailing the well dry once is adequate Purging will be performed utilizing a properly decontaminated stainless steel or Teflon bailer or the appropriate pump Utilization of a submersible pump is the preferable method of purging as repeatedly lowering the bailer into the monitoring well may oxygenate the formation waters and change the chemistry of the groundwater • CAG VSOP DOC